A new member has joined Eli and the Shane Gang! Junjie, once the protector of the Eastern Caverns, is a master of the slugslinging art of Slug Fu! But even with the power of five slingers, the Shane Gang find themselves in over their heads as they race across the 99 caverns in search of the legendary Elemental Slugs. The five Elementals are ancient slugs of great power, and the forebearers of all slugs found in Slugterra today. In the wrong hands, they could bring Slugterra to the brink of destruction. So when an evil alliance starts hunting down the Elementals, Eli and his friends — both old and new — take off in pursuit of the greatest threat their world has ever faced!
The movie starts with Redhook telling the tale of how Eli and the Shane Gang defeated The Goon and met Junjie to two children and a couple of slugs and inspires them to become slugslingers like the Shane Gang. Redhook wonders what 'heroic acts' the Shane Gang are up to now and the movie cuts to Eli sleeping on the hamper in the Shane Hideout while Burpy and the slugs are watching a Max Jackson Movie. Eli is asleep when he begins to have a nightmare-like vision of what was to come: Ghouled slugs, his father telling him to "Gather the Five", falling down a pit with Junjie, and a clawed hand coming up abruptly out of Dark Water. Eli wakes up and the slugs look to see what's wrong. Eli assures them it was nothing and walks away to see Junjie training with his slugs in the art of Slug Fu. Junjie asks Eli if he couldn't sleep either and describes a dream similar to Eli's. Eli is surprised at how he and Junjie have had similar dreams and Junjie says that they are more like premonitions.
After a rough sleep, Eli suggests a friendly morning duel. Junjie accepts and gets his slugs ready through an impressive show of his Slug Fu. Eli looks at his own slugs and is embarrassed to see them far-beyond ready for battle. Eli and Burpy try to get the slugs ready while Junjie is standing by unimpressed by Eli's lack of discipline with his slugs. When the duel begins, Eli fires Banger, who is easily defeated by Junjie's Frostcrawler and Junjie uses his Slug Fu to control the Frostcrawler to carry Eli over to him, and wins the duel. Eli congratulates him on winning, but Junjie hears a Rammstone firing and Eli assures him that it was nothing to worry about. Eli asks Junjie about him being able to tell what slug has been fired just from hearing it and Junjie says that it was part of his lifetime training to become the protector of the Eastern Realms.
The movie takes us to see the Shane Gang playing a game of racing their slugs around the vegetation of the cavern using remote control cars with the helmets on the slug's heads. Junjie asks what they're doing and Trixie describes the game followed by Kord. Junjie states that he does not need a remote to control his slugs and uses Slug Fu on his Tazerling to win the race against Stinky and Bludgeon. After the race, Junjie asks them "why" they do it and wonders if it takes away time for training. Trixie asks him if he's never played a game for fun and Junjie responds that he was always training to protect his caverns rather than have fun and play games with the other children. Pronto claims that if it wasn't for the Slug Fu, Stinky would've won for sure. Stinky is on Pronto's shoulder and shown to be violently twitching. He suddenly turns into a Flatulo Rex and attacks Pronto by biting him on the eyebrow. Bluster soon shares the same fate as do all the air slugs.
Eli and the Shane Gang go to the hideout to find all the air slugs have been ghouled suddenly and Eli tries to cure them with Doc, but as it was with Stinky, somehow the healing attack proves to be ineffective as a Tormato changes back into a Tempesto soon after. The Shane Gang wonders what happened when Trixie mentions a cavern that runs on wind-type slugs and the Shane Gang head over on their Mecha Beasts to save the caverns when the Shadow Clan show up in front of them and try to speak to Eli. Eli puts on his Shadow Talker while Kord asks for a translation. Instead of Eli, Junjie translates the message as the Shadow Clan wants the Shane Gang to follow them. When Eli objects, the Shadow Clan insists and mentions a message from Will Shane. Eli becomes interested and asks how they were going to get to where the message is. The Shadow Clan Leader lifts up a Shadow Walker and it begins to glow. Junjie translates for Kord that what was about to happen was "going to hurt."
The Shadow Walker starts to glow and reach up into the sky above the Shane Gang, and creates a vortex that lifts and takes the Shane Gang on a very dizzy ride. When they make it to the Dark Periphery Cavern, Junjie claims that "No training can prepare one for THAT" while Kord says his head hurt and Pronto barfed at the feet of the Shadow Clan who soon cringed at the sight. Eli asks for the message and a Fandango soon hops onto a platform and energizes it, transforming it into a large statue. Using more Fandangos, the Shadow Clan opened the tip of the statue to reveal another Enigmo slug. The Shane Gang are surprised as well as Mo is about the existence of another Enigmo while Pronto proves to be shocked that Will Shane would leave only an Enigmo as a message. Upon seeing the other Enigmo, Mo becomes entranced in its beauty and runs off to meet her while the Shane Gang watch in adoration except for Pronto, who gets jealous and claims 'he's cuter' than the Enigmo.
Eli wonders what the message was and the Shadow Clan leader takes the Enigmo and fires her on Eli, causing a huge barrier of light to form around Eli and the Shane Gang. After the Shadow Clan go to leave and help the other caverns, and a hologram of Will Shane appears before Eli. Eli calls out to him, to which Pronto tells him it's only a hologram. Will Shane apologizes for not being there and that he's proud of the man Eli has become. Like in Eli and Junjie's dreams, Will then reveals the truth about the five Elemental Slugs: Earth, Air, Energy, Water, and Fire. Will Shane tells the Shane Gang (really Eli) that if anything were to happen to one Elemental, the same thing would happen to the slugs of the same element or related to it, hence the sudden ghouling of the air slugs. Will also says that the Enigmo given to him has the map to each location that will only respond to Eli. Each time he asks to locate the Elemental he chooses, he'll be asked a question that only he and his father would know. Almost immediately after the initial message was over, the Shane Gang's water slugs turn into ghouls, including Beeker, who becomes an Aquafreak. Knowing that the Water Elemental Slug must be in trouble, Eli asks for the location of the Elemental. The hologram of Will Shane appears and mentions the Winters up in a cabin in the mountains on The Surface and asks what the name of Eli's sleigh was. Eli says 'Poopy Pants' and the location of the Water Elemental Slug is revealed on an island in the Cavern Seas. Eli commences the race for the Elemental Slugs.
When the Shane Gang arrive on the scene, the Cavern Seas is corrupted and instead has been turned into a sea of Dark Water while the vegetation has turned black and grown thorns. Pronto asks "What has HAPPENED to this place?" to which Eli believes it is because the Elemental Slugs are being ghouled that is leading to the dark transformation of SlugTerra. Just then, the Shane Gang are attacked by Darkbane and the Goon, who has found a new host slinger. The Goon says that the Shane Gang are too late in rescuing the Air Elemental Slug and shows it in a new ghouled form. Junjie claims he does not know of the Darkbane, but he knows plenty about The Goon. The Goon says that his "associate" will return soon with the Water Elemental Slug. Eli says he needs to get to the island to stop The Goon's "associate" and Kord makes an opening for Eli using a Crystalyd slug named Digger, and so Eli and Burpy sneak past them and fly over towards the island.
Meanwhile, the Shane Gang are still fighting fiercely against the Darkbane. Kord tries to push the Goon back on his host slinger, but somehow the slinger's body dodges it and frustrates Kord. Junjie tries to tell Kord to control his slugs using Slugfu, but that only frustrates Kord further into yelling off Junjie's plan to the enemy by accident. The Goon remarks on Junjie's plan, saying that his tactic won't work on his new host slinger. As The Goon plans to destroy Eli, he notices he's gone.
At the island location of the Water Elemental Slug, Eli, and Burpy seem to recognize the location somewhat through the ghouled transformation. They both wonder into a cave where the Water Elemental is supposed to reside. When they notice bubbles coming up a pool of Dark Water, the clawed hand from Eli's dream appears and a dark voice confirms Eli's worst fear: that the Water Elemental Slug has been ghouled. Eli then tells us that the dark voice belongs to none other than Dr. Blakk and the audiences sees that he's gone through a "massive" transformation. He now has larger muscles, giant claws infused with dark energy, sharp teeth, tusks on the edges of his chin, horns on his forehead, dark red eyes, and has grown into the size of a Cave Troll.
As Eli asks how he managed to escape the Deep Caverns, all that Dr. Blakk says is "My trip to the Deep Caverns was...invigorating". Eli tries to attack Dr. Blakk and get the Water Elemental Slug back, but Dr. Blakk caught the Rammstone Eli slung in his hand, and as it tried to escape, he used his dark claws to ghoul it in the palm of his hand.
Eli, surprised, tries to attack again, but Blakk loads his new Grimmstone into his Gattler and fires on Eli as Blakk at him with just one hand and knocks the Shane back. Blakk then grabs at Eli and is about to finish him when he has second thoughts. He then throws the Shane against a rock and proclaims he wants to see Eli's face as his whole world crumbles and everything he loves burns before him. Blakk then seals Eli inside the cave of the Water Elemental Slug.
Back on the beach, Blakk shows up on the shoreline with the ghouled Water Elemental and the rest of the Shane Gang sees his monstrous transformation. The Goon asks if Blakk eliminated Eli, and when the Goon sensed Eli's presence, Blakk tells him that he spared the Shane to watch him writhe in agony as Slugterra is destroyed before his eyes. The Goon scolds Blakk for not eliminating the Shane when he had the chance and the two get into an argument before the Darkbane defeat the Shane Gang.
As the Shane Gang are defeated, the Darkbane, Dr. Blakk, and the Goon escape to find the next Elemental. The Shane gang head to the edge of the beach to rescue Eli, but find the action unnecessary as Eli and Digger come up from the ground to warn his friends of Dr. Blakk.
When the Shane Gang tell their leader that they have already seen the new Dr. Blakk, they notice that Junjie is gone. The Dark Alliance tries to escape, and Junjie follows them in close pursuit and catches the Goon away from his associates. Being alone with the Goon and his new host slinger, Junjie tries to wake the host slinger from the Goon's control. As the Goon gloats on how under control he has the slinger, the Goon says his host slinger now is better than when Junjie was his host slinger. As Junjie tries to fight the Goon, the Goon pushes him back and runs away as Junjie is a witness. The Shane Gang catch up to Junjie and scold him for leaving while they were trying to rescue Eli, but Junjie excused himself by saying he was trying to retrieve the Water Elemental from the Goon. Eli then uses the Enigmo to find the location of the Earth Elemental, which upon answering that Will Shane brought his slugs to the surface, is revealed to live in Quartermain Cavern.
As the Shane Gang starts to head to the cavern Trixie suggests that the Goon is beating them because he is stealing the information from his head, however Junjie disagrees saying that the Goon knew about the Elementals prior to the Shadow Clan telling the gang about them, Eli agrees and they go to rescue the Earth Elemental.
As the Shane Gang arrive in Quartermain Cavern, they see it has been ghouled, like most of Slugterra now is. To get to the Earth Elemental, they must go through a mud river. Eli, Trixie, and Kord jump in, but Junjie and Pronto use Geoshards to make surfboards. The rest of the Shane Gang follows suit, and they soon find the Earth Elemental. Junjie uses a Rammstone to knock the Earth Elemental towards them, with his Slug-Fu. Trixie thinks he missed and fires an Armashelt. Seeing this problem, the Earth Elemental proceeds to jump before it is squashed in Velocimorph fury. The Earth Elemental falls in the mud, as does the Shane Gang after Pronto hits a rock. Trixie rescues the Earth Elemental, and the Shane Gang falls into a clearing after making a hole to fall through. Eli saves the Earth Elemental from the mud and the group uses Arachnets to patch up the giant hole, they begin celebrating, but Pronto points out that the webs aren't going to hold. Eli uses the Earth Elemental, much to Junjie's disapproval. The Earth Elemental not only stopped the flood, but it also cleaned the Shane Gang's clothes. Having officially rescued the Earth Elemental, the gang celebrates.
Meanwhile, in Quiet Lawn Cavern, Blakk and the Goon are destroying Quiet Lawn Cavern trying to find the Energy Elemental. Dr. Blakk insists that the elemental isn't there, and argues with the Goon that he should've listened to him and gine for the Earth Elemental, and the two have a brief argument before Redhook tries to stop them, only to get beat up by Blakk when they can't find the Energy Elemental.
When the Shane gang arrive, Blakk and the Goon are long gone, and there is major damage to the cavern from the rampage. Theyfind Redhook under a boulder, mortally wounded. Using a Thresher and Arachnet, they get Redhook out from beneath the boulder. Redhook thanks Eli, then succumbs to his injuries. Eli, believing Doc is capable of reversing Redhook's death, asks him to try and heal him, which he was successful in doing. After Redhook was revived, Junjie comments on Doc, saying Doc is something special. Kord immediately realizes that Doc is giving off the same kind of energy as the Earth Elemental. Trixie points out that Billy found him first. After the gang realizes that Doc is the Energy Elemental, Pronto reminds them that the status on the Fire Elemental is still unknown
The Shane Gang heads for Upright Cavern, and when Kord doesn't have jetpacks, Junjie decides him and Eli will use Burpy and Joo-Joo to get to the Elemental. When they get to the top, Eli points out that Darkbane can't fly. Junjie immediately spots the Elemental. The Darkbane, Goon and Blakk arrive riding Eels and chase off Junjie and Eli so the Goon can sneakily nab the Fire Elemental. All that Eli and Junjie could do was watch as Burpy and Joo-Joo turn into ghouls and force them off their backs. Without Infurnus', the pair fall down. Kord, Trixie, and Pronto manage save them with jetpacks, and a brief chase ensues, ending when they burst out of a hole in the wall. Pronto figures out they are in the The Jungle Cavern, which was also now ghouled.
The dark alliance is not far behind. They soon bust down the rocks and join the battle. In the midst of it, Blakk shot the Ghouled Air Elemental, which created a massive, permanent terraportal to the Deep Caverns which almost successfully sucks in the Shane Gang (Not counting Junjie who is sitting on the edge). Thanks to Junjie's smart thinking, Eli and the others escape the sink hole. At another point, Eli pretends Banger is the Earth Elemental using Junjie's Phosphoro as a distraction. Soon Eli comes up with a plan. Pronto drives Blakk away while Trixie and Kord take care of the Goon and the Darkbane. Then Junjie is supposed to guide Blakk to Eli when Kord alerts Junjie that Blakk doesn't have all the Elementals. The Goon attacks Eli, and Doc, having fallen out of his slug tube and becoming exposed, perfect for the Goon to ghoul him! Having to save Doc, Eli fires the Earth Elemntal to protect him, and the Goon decides to turn around and use his Ghoulgoyle attack on the Earth Elemental. At this point, Slugterra was beginning to succumb to the dark energy from all the ghouls. Shorthy after, the Goon confronts Eli about having the Energy Elemental, and Eli then confronts the Goon asking how he hacked into his father's hologram. The Goon them takes off his helmet, revealing a gray skinned, disheveled Will Shane as the Dark Slinger! Eli then fires Doc at the Goon releasing Will from his possession and also curing the Fire and Earth Elementals. Once Eli checks on his father, the two find Kord, Trixie, Pronto and Junjie and try the plan again, this time with two Shanes. First, there were a brief few moments of shock from the rest of the Shane Gang, however. This time the plan goes well. The Goon (who is now possessing Blakk) is yet again stopped, and this time the Goon is in Doc's healing blast, which drains all of his dark energy away and would've eventually died. While the Shane Gang are rejoicing, Blakk heals the Goon and the two of them try to hit all five elementals with one shot. Thanks to Will's quick thinking, he managed to throw himself and the villains into the Deep Caverns. As Eli becomes hysterical seeing this, Junjie tells him to put aside his emotions to save Slugterra. Reluctantly, the Shane Gang fire the Elementals into the air and reverse the damage to Slugterra. Now, they agree to find and rescue Will Shane.
- Eli Shane
- Kord Zane
- Dr. Blakk in a new monster-ized form.
- Will Shane
- The 99 Caverns
- The Jungle Cavern
- A Shadow Clan village near Xanadu Basin
- Wind-Farm Cavern (Mentioned only)
- Wild Spores Cavern
- Locations of 4 of the 5 Elemental Slugs
- The Eastern Caverns (Mentioned only)
- During post-production the film was titled "Slugterra: The Power of Five".
- This marks the return of Dr. Blakk but he is in a new form.
- Will Shane is revealed to be alive.
- This is the first time Will and Eli interact with each other in the series.
- This is the second time a new member joins The Shane Gang the first time was The New Kid Part 1 and 2.
- Blakk's Gattler is different to the one he uses in the series.
- this is the first time in the series anyone called boon docs by there real names in any other episode they called them "healers".
- Slugterra: Return of the Elementals won the Leo Award 2015 for Best Overall Sound in an Animation Program or Series. 
- Redhook tells two kids and a few slugs about how the Shane Gang defeats The Goon and gets the new member Junjie from the previous movie "Slugterra: Ghoul from Beyond".
- Trixie says that they thought that they have the only Enigmo slug as stated in "Endangered Species".
- Dr. Blakk says that his trip to The Deep Caverns is invigorating since he was thrown into The Deep Caverns at the end of "Light as Day".
- Trixie mentions Tom Por, Dana Por's father who was mentioned & seen in a flashback in "Inheritance", and their former friendish.
- "The Burning World", a term used by Slugterreans to refer to The Surface in "A Distant Shore", is used by Redhook.
- Redhook mentions the legend of "odorless plumbing" again since "The Hard Part".
- Kord's motion detector mod from "It Comes by Night" is used again and it is been calibrated to pick up the unique energy signature emitted by The Elemental Slugs.
- Eli tells Junjie that Doc is a Guardian Slug, a status that Doc achieves in "What Lies Beneath".
- Trixie guesses that The Hooligang probably found Doc first in Quiet Lawn Cavern before they duel with Eli in "The Slugout" since Billy used to have Doc in his arsenal in that episode.
- Kord creates Jetpacks again since "The Thrill of the Game".
- Eli tells Junjie that he sort of just figured out how to fly on an Infurnus as he only found out in "Light as Day".
- Pronto mentions Twist, who was once a member in the Shane Gang but later betrayed them in "The New Kid Part 2".
- When the Shane Gang crash lands in The Jungle Cavern, they recognize the place as they have been there in "Endangered Species".
- Junjie speaks Cantonese when he is commanding his slugs in a friendly duel with Eli. Cantonese is a variation of the Chinese language spoken in the city of Guangzhou in southeastern China. It is similar to Mandarin, but with different pronunciation, grammar and lexicon. Moreover, Cantonese is the most common Chinese variety spoken among Chinese Canadians (in which Vincent Tong, the voice actor of Junjie, is a Chinese Canadian. Since Junjie looks like a South-Asian orient, this could explain why he speaks Cantonese, adding the fact that Chinese from Southern China are common across Southeast Asia and North America).
- When Suds in Pronto's arsenal was ghouled (because of the Water Elemental), Stinky was normal (and the Air Elemental was ghouled).
- Buzzsaw looks like Butch.
- The Shane Gang shoot a Bubbaleone when the Water Elemental Slug is ghouled.
- There is a Ghoul from Beyond scene.
- Trixie shoots Bluster when the Air Elemental Slug is ghouled.
- Dr.Blakk's eyes were not ghouled in one scene even though the Goon had ghouled him.
The film had a limited theatrical on August 2, 2014 in the United States. The film also had a limited theatrical in Canada on August 21 and 23, 2014.
The film will be purchasable on Amazon in US and Canada on Cineplex/Walmart on 16 September 2014.
The film first premiered in United States of America on Disney XD USA on August 29, 2014 and Canada on September 13 2014.