Final Crisis: Legion of Three Worlds #3

Synopsis

Shadow Lass and Mon-El light the fire under Sodam Yat, then head to Earth and the battle between Superboy-Prime's Legion of Super-Villains and the Legion of Super-Heroes. The battle is joined first, however, by the Legions of two other universes. Meanwhile, the team on the mission to the past retrieves a hair from Lex Luthor. Taking a select group of Legionnaires to headquarters, Brainiac 5 relates the story of the first time these three Legions met. Getting wind of what Brainiac 5 is really up to, Superboy-Prime heads to Legion HQ just in time to witness the return of Bart Allen, Kid Flash.