As Michael, Lincoln and the remaining Ogygia gang try to escape Yemen, they find themselves racing through the desert from a vengeful Cyclops.
This special crossover episode sees Supergirl, The Flash, Green Arrow and DC's Legends of Tomorrow unite against an alien race called the Dominators.
When the body of a decapitated paramedic seemingly comes back to life, the agents begin to suspect the man may be an evolutionary freak capable of regeneration.