The next morning he feels sick and goes to the hospital. When they tell him he's been poisoned and is gonna die in a few days he freaks out - "This is fantastic! This is the most ridiculous thing! This is impossible! You're nothing but a coupla phonies!" - and goes running down the street like a madman. Once he calms down he gets pissed and goes out in search of his killer.
Not quite as hard-boiled as you would hope but still an awesome movie from beginning to end without a minute wasted. Highly recommended.
Notice the names: Ernest Laszlo (Cinematographer), Marty Moss (Assistant Director) and Russell Rouse (Writer).