Decades prior to the start of the film, the Zenith team are five young superheroes who fought to protect the world from evil, led by Jack Shepard ("Captain Zoom") and his older brother Connor Shepard ("Concussion"). The American military sought to enhance the team's powers using an experimental form of radiation called "Gamma-13". This made Zoom faster and stronger, but the gamma turned Concussion to the dark side. Thinking Zoom and the team betrayed him, Concussion killed his teammates Marksman, Ace, and Daravia. Concussion was believed to have been destroyed by Zoom at the cost of his powers, but was sent into another dimension instead.