Spike learns the truth about Gren—turns out he was a soldier in the Titan War who got experimented on by military doctors with female hormones, part of some weapons program that Vicious oversaw. The drugs transformed Gren's body and destroyed his sense of self, leaving him hunting for revenge against the man who ruined him. Meanwhile, Faye ends up caught in the crossfire as Vicious arrives on Callisto to use Gren as a pawn in his power struggle with the Red Dragon Syndicate.
The confrontation between Gren and Vicious goes brutal, with Spike getting pulled into the fight. After a violent showdown with Vicious, Gren makes his choice—he launches himself into space in a ship that becomes his tomb, finding freedom the only way he can. Spike realizes the woman he saw wasn't Julia after all, just another dead end in his search. Both Spike and Faye head back to the Bebop empty-handed, carrying the weight of what went down on Callisto's frozen surface.
"Space Lion" plays during Gren's final moments, creating one of the series' most heartbreaking scenes.
"You're gonna carry that weight."