A doctor commits euthanasia on his dying friend and then pursues an affair with the latter's wife, causing a small New England town to suspect him of plotting it as a murder.

City doctor Guy Montford returns to his Massachusetts seaside hometown at the request of his best friend, Larry McFie, who is dying of cancer. Upon arriving, he visits the cemetery, where he barely acknowledges his mother's grave, but takes off his hat in respect at the graveside of his father. In town, Guy greets Bert Mosley, a sleazy lawyer who is running for district attorney, and Fran, a young nurse who has long admired Guy. Dr. Sol Kelsey, a hospital administrator and family friend, adds Guy to his staff, allowing him to oversee Larry's treatment. However, Larry's father, Sam McFie, is unhappy with Guy's participation, claiming he opposes Guy treating Larry's illness, while simultaneously railing at Guy to save his son. While suffering great pain as his life ebbs away, Larry is concerned about his wife Margaret, whom Guy has not met, and hopes that Guy and Mar will marry after he is dead. When Mar, who is deeply in love with her husband, arrives and introduces herself, Guy is instantly drawn to her. Admitting that she has been drinking more than usual to escape bad dreams, she invites him out for a martini. At the tavern, Mar asks how long Larry has to live, but Guy refuses to give up on a patient by forecasting his death. After Guy retires to his empty family house, the town alcoholic, Stew Schaeffer, knocks on the door to ask forgiveness, but Guy angrily shuts him out. Another day, Guy responds to an emergency call involving a motel fire, where he treats Bert and Fran, who had registered under assumed names as a married couple, for smoke inhalation. Bert worries that their rendezvous will become public and jeopardize his chances for election. More concerned about Fran, who could lose her job if caught in an illicit affair, Guy tells nosy reporter Parker Welk that she is working as his nurse. When Fran worries that Guy will think she is a "tramp," he reassures her and afterward she breaks off with Bert. At Larry's urging, Guy and Mar make plans to go sailing, but Mar, uncomfortable with Guy, wants to break the date. She tells him she has nightmares about a crying baby, which she believes she will never be able to have once Larry dies. One night, Larry, hemorrhaging and in great pain, calls Guy to his hospital bed and begs him to help him die. Guy argues that a new miracle drug might be available soon and is distressed that he can do nothing for his friend. He later tells Sol that, hoping for a cure, he will be meeting with a cancer specialist in Boston, and mentions Larry's plea for euthanasia. Fran, now off-duty, invites Guy to her quarters, where she confesses her love and offers what "comfort" she can give. Unable to reciprocate her feelings, Guy leaves. In the parking lot, Sam harasses Guy, insisting that he "do something" and then, illogically, "fires" him as Larry's doctor. When he gets home, Mar comes to urge him to stay on Larry's case. Soon after, Stew arrives and Guy rudely throws him out of the house, shocking Mar, who accuses Guy of being cruel. Guy confides that, as a child, he saw Stew and his mother in bed and told his father, who then committed suicide. Agitated by the past and present, Guy runs from the house and Mar follows him to his boat, where they make love. The next day, she leaves town. Soon after, Parker threaten to publish an account of the motel incident in his paper unless Fran poses for nude photographs. She agrees, but when Bert discovers her posing for Parker, he knocks him out. Guy, who is summoned to treat Parker's injury, finds Parker's provocative photographs and threatens to show it to Parker's wife if he troubles Fran again. After learning from the cancer specialist that there is no cure in the offing for Larry, Guy gets drunk at a Boston hotel, where Mar, who has become pregnant from their one encounter, seeks him out after deciding against an abortion. Guy proclaims he loves her, but she still loves Larry and rents a separate room. At the hospital, tormented by Larry's pain, Guy gives him an overdose of morphine. After Larry dies, Mar is relieved that he no longer has to suffer. Guy then confesses that he, not God, released Larry from his pain. Seeing Guy and Mar together, Fran guesses that they are in love. When she discovers morphine missing from the hospital inventory, she becomes distraught and tells Bert about the missing morphine. Recognizing an opportunity to try a "big" case that will help him get elected, Bert urges Fran to report the missing drug. The report prompts an autopsy and when the results cast suspicion on Guy, the local sheriff, a longtime family friend, must arrest him. Telling Guy that he has evidence proving that he and Mar stayed at the same hotel, Bert blackmails Guy into hiring him as attorney. During the trial, Guy's conviction seems certain, after Sam falsely states that Larry expressed fear that Guy would kill him. Aware that the townspeople want a reason to acquit Guy, Bert asks Mar to sacrifice her reputation by presenting herself as an "immoral outsider" who inspired Guy to murder, but Guy will not allow it. After a conversation with the local priest, Guy begins to question his decision to end Larry's life. The next day, Bert calls Sol to the stand, who testifies that he heard Larry, in pain and semi-consciousness, begging, "Guy, I beg you to do it. Kill me. Do it now." After Sol states that Sam has been diagnosed for years as emotionally disturbed, the jury acquits Guy. Afterward, Mar confesses to Guy that she loves him, but believes that their feelings of guilt would cripple their relationship. Guy, however, feels more certain that one day he and Mar will see each other again and what has happened will not matter, because they love each other.