Grimmel captures Hiccup and controls him with a purple substance he uses for controlling the Death Grippers. With Hiccup under the control of Grimmel. Toothless, The Lightfury, Astrid and the gang need to find him and save him from Grimmel's clutches.
This is the story of Sigma's upbringing and development. He learns to speak and lives among humans in his host park, Prehistoric Worlds Resort. PWR is a successful, Jurassic World-like park who has many accurate dinosaurs on display. Sigma didn't turn out as accurate as the team who created him would've hoped, but...