Magic and science collide, placing Lex Luthor and Flash's minds in each other's body. The Justice League must now contain a super-speed powered Luthor on the Watchtower while Flash tries to hide the reversal from the Secret Society.

Supergirl, Green Lantern and Green Arrow are kidnapped and taken to the 31st Century by Brainiac 5 and Bouncing Boy of the Legion of Super-Heroes, where Supergirl is destined to embark on her very last mission – a battle against the Fatal Five and the Legion itself.