Ryan performs a magic trick with fellow YouTuber Dan Rhodes in a livestream, which is interrupted when Ryan finds out that his sisters, Emma and Kate, stole goo needed for the trick. After confronting his sisters for vandalizing his items, Ryan and his friend Aiden head to Dabgib Comics, where after completing a favor for Clark, the store's owner, they are both given access to a secret room in the store, where Ryan finds a comic book plagiarizing his work. Ryan steals the comic and returns home, where he sees that Emma and Kate have vandalized another one of his toys. He threatens to never play with his sisters again and storms away. Emma and Kate then notice the comic book starting to come to life, and upon opening the book, they are told by a unicorn—who is actually one of the book's villains, Dark Titan, in disguise—to enter the book so that they can impress Ryan. When Ryan returns to apologize to his sisters, he finds out that they have entered the comic book, and enters the comic book world on his own to save his sisters, leaving Aiden behind to prevent Ryan's father from realizing that his children have disappeared.
Upon entering the Titan Universe, Ryan transforms into the animated superhero Red Titan, gaining superpowers that he uses to fight off a horde of robots that attempt to capture him. Ryan is saved by a bat named Stella, and the two team up to save Emma, Kate, and the Titan Universe. Meanwhile, Emma and Kate are being held captive by Dark Titan, locked away in a dungeon with Combo Panda and Alpha Lexa, two superheroes from the Titan Universe. Ryan encounters and defeats Dark Titan, allowing everyone in the dungeon to escape. Emma and Kate, who have also gained superpowers, use their telepathy to devise a plan and help out Ryan by tricking Dark Titan into destroying his lair and becoming defeated in the process. After escaping, Ryan tells Emma and Kate that they are too young to fight the "Big Bad", the true villain of the Titan Universe, and advises them to not join him.
It is revealed that Big Bad is planning to cause a volcanic eruption that will destroy the Titan Universe by putting Mentos into lava. The volcano slowly starts to erupt, becoming an obstacle for Ryan and his team. After being saved by Ryan, Emma and Kate tell him that they are being underestimated, only for everyone to be captured by Big Bad and his henchmen. At his lair, Big Bad explains his plot to destroy the Titan Universe and kill the heroes in the process. Big Bad reveals that he is actually Clark, and that he made the comic book himself to kill Ryan, as Clark's little sister, Mia, stopped playing with him in favor of watching Ryan's videos. As Ryan and Big Bad battle each other, Aiden retrieves some of Ryan's toys and sends them to the Titan Universe, bringing them to life and serving as backup for Ryan. After defeating Big Bad, Ryan and his sisters say goodbye to the other heroes as they leave the Titan Universe. Back in the real world, they completely hide their adventure from their parents and begin to have fun outside.
