Two veteran private eyes trigger a criminal reign of terror with their search for a missing girl.

In Los Angeles, private detectives Al Hickey and Frank Boggs bemoan their financial woes and their pathetic personal lives. The African-American Hickey is separated from his wife Nyona while the sexually conflicted, alcoholic Boggs is unhappily divorced from his stripper wife Edith. One morning, while Hickey meets a new client, the effeminate Rice, at the beach, Brill, a leading gangster, has a conference with his men Ballard and Bernie. The gangsters are angered that a woman, Mary Jane Bauer, has been sending $1,000 bills to local fences in hopes of selling the currency, which totals more than $400,000. The money was stolen from a Pittsburgh bank in a robbery bankrolled by Brill's syndicate, although all of the robbers were killed and the loot mysteriously disappeared. At the beach, Rice tells Hickey that he is to make discreet inquiries to find Mary Jane, his missing girl friend. Back at their shabby office, Hickey informs Boggs about their "sweet lips" client, and they divide the names given to them by Rice as potential leads, with Hickey to question Clifton Farrow and Boggs to find Tina Swope, Mary Jane's former friend. The next morning, Mary Jane shoots Farrow, a fence who was blackmailing her, just before Hickey arrives. Hickey reports finding the body to policemen Papadakis and Al Shaw, who are irritated by his sarcastic manner. At their usual haunt that night, Boggs tells Hickey that Tina has not seen Mary Jane recently, although she did relate that Mary Jane's boyfriend, Quemando, was imprisoned for armed robbery several years earlier. That night, Hickey visits Nyona, and despite their mutual love, their lack of communication forces them apart. Meanwhile, Rice, who is an underworld fence, is forced to give a list of other fences to Brill, and although he offers Brill the same names that he gave to Hickey, he denies having heard of Mary Jane. Brill then orders hired killer Monte to assemble his team, consisting of psychopathic bodybuilder Fatboy and gun expert Nick. The next day, Boggs searches Farrow's apartment and finds a cryptic note about an upcoming Rams-Falcons football game, as well as two $1,000 bills. Hickey, discouraged that Rice has disconnected his answering service, insists that they turn over the evidence to Papadakis to keep him "sweet," although they keep a copy of the note and continue to follow the leads. While they visit Quemando's brother, who runs a nursery, Mary Jane visits the still-imprisoned Quemando, who is actually her husband. After learning nothing from the florist, Hickey and Boggs go to an address listed on Farrow's note. The switchboard operator there tells them that the room in question is rented to a woman named Mary Florida, although she has disappeared. While the detectives search the apartment, finding a note with the same numbers in reference to the football game, Monte and his hoodlums arrive. The operator warns the detectives, who finally escape when Boggs blows up the killers' car. At the police station, meanwhile, Papadakis receives confirmation that the $1,000 bills from Farrow's apartment were from the Pittsburgh bank robbery. In the morning, Hickey returns to the nursery, where he discovers that Quemando's brother has been murdered by Brill's "torpedoes." After Hickey and Boggs are questioned at the police station, Papadakis tells them about the bank robbery, and that there is a $25,000 reward for the return of the loot. Believing that Mary Jane intends to meet a buyer at the Coliseum, Boggs insists on attending the Rams-Falcons game, although when no one shows up in the seats listed on the notes, Hickey deduces that the exchange is to occur the next day, and so they return the following afternoon. Also watching the stadium are Monte, Fatboy and Nick, and when the bagman who is to buy the currency arrives, a chase and shootout ensue. The bagman is killed and after the three hoodlums retrieve his money, they escape, leaving Hickey and Boggs to be interrogated by the police again. After being dismissed by Papadakis, Hickey and Boggs split up, with Boggs going to question Elena Cole, another name on Farrow's list. At Cole's home, Boggs is greeted by Rice, but, not having met him earlier, does not recognize him. Boggs is bemused to see that the mansion is being stripped by members of the black militant organization headed by Mr. Leroy, Rice's business partner. He learns little of value, however, and when he next meets with Hickey, he is drunk and dejected that they have no leads. Hickey attempts to sober up his partner and tells him that they have received a call from Mary Jane, who professed to be frightened and eager to turn over the loot in order to be free from Brill's syndicate. Leery, Hickey and Boggs attend that night's Dodgers baseball game, then wait in the parking lot for Mary Jane. Instead, they are met by Monte and his men, who have also been summoned by the double-crossing Mary Jane in an attempt to get rid of as many of the factions pursuing her as possible. Rice, who has learned about the drop, sends business partner Phillip Bledsoe, dressed in women's clothes and posing as Mary Jane, to distract the gangsters, and during another blazing shootout, Bledsoe and Nick are killed, Boggs's car explodes and the detectives are arrested. After being bailed out, Hickey complains to Boggs that they should quit, as their profession is "not about anything" anymore, but Boggs retorts that it is about $400,000. Soon after, Hickey gets the drunken Boggs out of a strip club in which Edith is performing and proffers an emotional speech that they must stick together. After pursuing more leads, Boggs discovers that his home has been vandalized and calls Hickey to warn him. At Hickey's apartment, however, the detective mournfully stares at Nyona's body, as she has been brutally murdered by Brill's thugs. That night, Quemando, who orchestrated the Pittsburgh robbery from prison, with Mary Jane carrying out his orders to steal the loot, arranges with Brill to be forgiven for the double-cross by arranging a drop with Rice and Leroy, during which the fences will be killed and the money given to the gangsters. The next day, Boggs learns that Mary Jane is actually Mary Florida Quemando, and while talking to the grieving Hickey, speculates about her and Quemando's roles in the bank heist. When Hickey refuses to be engaged, Boggs gives him the same speech about partnership and states that by following the money, he can avenge Nyona's murder. Soon after, the two confront Quemando, who leads them to Rice and Leroy. With the gun-toting Hickey and Boggs in their cars, the men drive to the isolated beach where Mary Jane is to meet them. Mary Jane lands in a small airplane and after exchanging the loot for the clean currency, she and Quemando are preparing to leave when a helicopter, piloted by Monte and carrying Ballard and Fatboy, arrives. The gangsters shoot Rice, Leroy and Leroy's men, then also kill Quemando and Mary Jane. After Fatboy disembarks to retrieve the money, Boggs and Hickey spring out of hiding and in the ensuing shootout, destroy the helicopter. The enraged Fatboy comes after them with a piece of the fiery wreckage, but Hickey brings him down with a single shot. Taking the gun from his partner's hand, Boggs then helps Hickey up, and as they are walking away with the money, agrees with him that their business is still not about anything.