Consider this plot: The novel opens outside a club in Los Angeles called the Dancers. It is late October or early November; no year is given, but internal evidence and the publication date of the novel places it between 1950 and 1952. Philip Marlowe meets a drunk named Terry Lennox, who has scars on one side of his face. They forge an uneasy friendship over the next few months, having drinks, especially gimlets, together at bars. In June, Lennox shows up late one night at Marlowe's home in "a great deal of trouble" and needing a ride to the airport across the border in Tijuana, Mexico. Marlowe agrees as long as Lennox does not tell him any details of why he is running. He later finds $500 left to him by Terry.

On his return to Los Angeles, Marlowe learns that Lennox's wife Sylvia was found dead and that she had died before Lennox fled. Marlowe is arrested for aiding a suspected murderer after refusing to cooperate with investigators, who want him to confess that he helped Lennox flee. After three days of antagonizing his interrogators, Marlowe is released, the police explaining that Lennox has been reported to have committed suicide in a small town in Mexico with a written confession by his side. Marlowe gets home to find a cryptic letter from Lennox containing a "portrait of Madison" (a $5,000 bill).
A "portrait of Madison"

Marlowe gets a call from Howard Spencer, a New York publisher, who asks him to investigate a case. One of Spencer's best writers, Roger Wade, has a drinking problem and has been missing for three days. Initially Marlowe refuses but after Wade's wife, Eileen, also asks for Marlowe's help, he consents. Marlowe finally finds Wade in a makeshift detox facility in an isolated and soon-to-be-abandoned ranch. He takes his fee, but the Wades' stories do not match.

The Wades each try to convince Marlowe to stay at their house to keep Roger writing instead of drinking, and, though he refuses, he ends up making further trips to the house at their behest. He is invited to an awkward cocktail party, where Dr. Edward Loring threatens Wade to leave his wife Linda alone. Marlowe had accidentally met Mrs. Loring previously at a bar, where they were drinking gimlets together in memory of Terry Lennox. It turns out Linda Loring is Sylvia Lennox's sister and had known Terry well.

After being called by a drunk and disoriented Roger, he arrives to find Wade passed out in the grass with a cut on his head and Mrs. Wade oddly uninterested in her husband's welfare. He is put to bed with a head wound from a likely fall. Dr. Loring is called and examines Wade briefly, not hiding his contempt. Wade wakes up and begs Marlowe to remove and destroy some typewritten pages in his study he wrote while drunk, not wanting his wife to read them.

Marlowe removes and reads the pages, finding a cryptic self-analysis by Wade which hints at repressed trauma he doesn't quite understand alongside a clear statement that “once a good man died" for him. Marlowe keeps this evidence. He hears a shot upstairs and rushes up to find the couple struggling over a gun in Roger's bedroom, the bullet having gone harmlessly into the ceiling. Marlowe sits with Roger until the latter has taken some sleeping pills. As he is leaving, a distraught half-naked Eileen enters a sort of trance and attempts to seduce Marlowe, thinking him to be a former lover of hers who died in the Second World War. Marlowe refuses with difficulty and crashes on the couch downstairs, getting completely drunk so that he passes out instead of being tempted to go back to Eileen's room. The Wades' houseboy Candy makes threats against Marlowe. The next morning Eileen behaves normally and Marlowe leaves.

Marlowe is repeatedly threatened to cease his continued investigation of the Lennox case, first by a gangster friend of Lennox's named Mendy Menendez, then by Lennox's wealthy father-in-law Harlan Potter, by his old friend Bernie Ohls from the LAPD, by Candy, and by Mrs. Wade. Through his own hunches and inquiries, Marlowe also learns that Terry Lennox had previously lived as Paul Marston, who had married and spent some time in England.

Roger calls Marlowe again, inviting him to the Wades' for lunch. After indulging in self-pity over his writing difficulties, he posits that he's an alcoholic because he's trying to find answers to the trauma in his past, offers Marlowe a check of $1,000, then proceeds to drink himself into a stupor. Marlowe asks him if he ever knew someone named Paul Marston, and with an effort Roger says no. Marlowe takes a walk outside. When he returns, Eileen is ringing the doorbell, having forgotten her key. Marlowe finds Roger dead on the couch, apparently from suicide, but Eileen accuses Marlowe of killing her husband. Candy fabricates a story of Marlowe sleeping with Mrs. Wade to implicate Marlowe, believing him to be guilty, but his claims are undermined in an interrogation. The police do not hold Marlowe.

Marlowe receives a call from Spencer regarding Wade's death and bullies Spencer into taking him to see Mrs. Wade. Once there, Marlowe grills her on the death of Sylvia Lennox. Eileen first tries to blame it all on Roger but Marlowe pokes holes in her story, arguing that she killed both Mrs. Lennox and Roger Wade and that Lennox was her first husband, presumed killed while serving with the British Commandos in Norway during the war. Eileen Wade leaves with no response. The next morning, Marlowe learns that she has killed herself by overdosing on painkillers, leaving a note describing the affair Mrs. Lennox was having with her husband and confessing to killing them both in a jealous rage.

Marlowe refuses to let the story lie, and when the authorities decide to forgo an inquest because it will show them up, he steals a photostat of Eileen's confession from the police. Marlowe contacts a reporter he knows in order to make sure the confession is printed, even though the reporter warns him that he'll make numerous enemies by doing so. Marlowe replies that he has been trying to say goodbye to Terry Lennox for "a long, long time." A few days later Marlowe is assaulted by Menendez, who is then arrested by Ohls in a setup. Ohls explains that Marlowe was intentionally left in a position to steal a photostat because the police wanted to trap Menendez in a felony, and Ohls knew that Marlowe's scruples and stubbornness would lead him to do the best he could to clear Lennox's name.

Mrs. Linda Loring had called Marlowe previously, informing him that she is getting a divorce from her husband Dr. Loring, who subsequently had written massive doses of Demerol to the late Mrs. Wade, allowing her to overdose. Linda pays a visit to Marlowe's house with an overnight bag, and they drink champagne together. She stays for the night and even proposes a marriage to Marlowe. In the morning they part amicably, Linda leaving for Paris.

Later, Marlowe is visited by a Mexican man who claims to have been present when Lennox was killed in his hotel room. Marlowe listens to his story but rejects it and offers his own version, ending with the revelation the Mexican man is none other than Lennox himself, who has had cosmetic surgery. Lennox attempts to make amends for the trouble he has caused Marlowe but is rebuffed. While Marlowe claims that while he doesn't judge him for what he did, he returns the $5,000 bill and says Lennox is "not here anymore." Lennox is hurt by this and leaves after saying goodbye. The novel ends with Marlowe listening to Lennox leave and faintly hoping he might return but instead explaining that he never saw him again. the end. list all the plot holes and dangling, unexplained or pointless details.