After getting rid of Carmen, Marlowe threatens Brody with Carmen's gun, demanding to know where Brody works (he works in insurance for a man named Puss Walgreen).
Marlowe wants to know how Brody got Carmen's photos, and Brody claims that he was watching Geiger's house because he wanted to get into Geiger's racket.
Brody explains that he saw Vivian's Buick parked nearby. When he heard shots coming from the house, he saw Owen Taylor run outside and drive off in the Buick. So Brody tailed Taylor until the car skidded off the road.
Then he pretended to be a cop, hit Taylor on the head and stole the plateholder from him, not knowing what the negatives held. After developing the negatives, Brody realized that Geiger was the one who had been shot since he didn't turn up to work the next day. That was when Brody decided to move in on Geiger's porn racket.
Marlowe appears to buy Brody's story, at least the part about not murdering Geiger. But Marlowe still can't figure out who hid Geiger's body.
The doorbell rings again. (We sense danger ahead).
Brody opens the door. BANG! A shot is fired and Brody drops dead.
Marlowe chases after the gunman and finally catches up to a handsome dark-haired boy—it's the "punk kid" that Brody mentioned who works at Geiger's store. Marlowe figures out that the kid is Geiger's lover and had shot Brody thinking that Brody had killed Geiger.
Marlowe finally gets the kid to tell him that his name is Carol Lundgren. Marlowe tells Carol that he shot the wrong guy. Bummer, dude.