Racketeer Eddie Mars’s “best boy,” Lash Canino is a lethal hired assassin. He kills the grifter Harry Jones, who’d been snooping into Mars’s business, by lacing his whiskey with cyanide. Canino also keeps Mars’s wife Mona in hiding, to keep up the pretense that she ran away with the missing Rusty Regan. When private detective Philip Marlowe finds Mona’s hiding place, he has to kill Canino to protect himself and Mona, who helps Marlowe to escape.