Ernie Driscoll (Payne) is a taxi driver and former heavyweight boxer who took the former job after having to abandon the latter due to an eye injury sustained in his last fight. His would-be stage actress wife Pauline (Castle) has grown increasingly resentful toward him for supposedly holding them both back with his lowly labor and misplaced nostalgia.
Ernie's attempt to make things up to her by suggesting they start a family gets nipped in the bud when he comes across his wife kissing a man named Victor Rawlins (Dexter). Unknown to Ernie, who angrily drives off when the adulterous duo approach his cab, Victor is a thief who plans to run off with Pauline that night once he closes a $50,000 deal with his fellow criminals. Ernie's night gets worse when his friend Linda James (Keyes), an actual stage actress, and the team behind the play in which she wants a role enact an elaborate practical joke on him to see if her acting's up to snuff; the now doubly enraged Ernie beats several of the men before leaving and gets the police called on him for assault.
The cherry on top of Ernie's bad night is when Victor, whose money deal goes sour in part due to Pauline's presence, kills Pauline and sneaks her body into the back of Ernie's cab. Now Ernie must work with Stan Hogan (Faylen), his cab company dispatcher friend, and Linda, who seeks to make up for her part in the cruel prank, in order to clear his name before the police find him and/or Victor leaves the country.
99 River Street has examples of:
- Asshole Victim: Pauline was such an unlikable woman that Ernie and Linda are less grieved over her death than fearful that they'll be blamed for it.
- Attempted Rape: Supposedly what led Linda to "kill" the producer.
- The Big Rotten Apple
- Chekhov's Boomerang: Linda's acting skills are brought up during her introductory scene before being put into play when she and the theater production staff prank Ernie. She later uses her acting to lure Victor outside.
- Extremely Short Timespan: Excluding the Time Skips at the beginning and end, the entire film takes place over just a few hours in one night.
- From Bad to Worse: Ernie starts off having merely a generic crummy day due to his wife's berating and his longing for his boxing days. Then he sees Pauline kissing Victor. Then Linda and the theater guys play their prank on him. Then he punches the theater guys out of anger, incurring assault charges. Then he finds Pauline's body dumped in the back of his cab.
- I Coulda Been a Contender!: Ernie had to give up boxing due to an eye injury which could have left him blind if he were ever hit there again too hard.
- Large Ham: Linda really puts her all into her acting during the theater scene and the cafe scene. It provides quite a contrast with her more demure real self.
- Mission Control: Stan uses his position as dispatcher to gather address information for Ernie while keeping the cops off his friend's tail.
- Mugging the Monster: Mickey finds out the hard way that when you hold a former boxer at gunpoint and then let down your guard, you are inviting yourself to a No-Holds-Barred Beatdown.