Leslie Crosbie [Bette Davis] is the wife of a British rubber plantation manager in Malaya, and she shoots dead Geoffrey Hammond [David Newell], a well-known member of the expatriate community. Leslie tells the servant to send for the new district officer and her husband Robert Crosbie [Herbert Marshall], who is loading rubber for shipment. Crosbie returns, delivered by his attorney, a close family friend. Leslie claims that she killed Hammond to save her honor.
She is placed under arrest, jailed in Singapore, and charged with murder. Her eventual acquittal seems a foregone conclusion, as the White community not only believes her story but feels she had acted heroically. Only the attorney, Howard Joyce [James Stephenson], harbors suspicion. His clerk, Ong Chi Seng [Victor Sen Yung], tells him a letter exists that Leslie wrote to Hammond the day of the shooting, imploring him to come that night while Robert was away.
Ong tells Joyce that the original is in the possession of Hammond's widow, Mrs. Hammond [Gale Sondergaard], a Eurasian woman who lives in the Chinese quarter. He shows Joyce a copy, revealing Leslie's clear culpability in her lover's murder, and conveys that the original is for sale, at a staggering price. Joyce then confronts Leslie, who first denies then breaks down and confesses to having written it. She manipulates him into agreeing to buy it back despite the risk to his career.
Joyce tells Robert about the letter without divulging its content or true price, which will exhaust nearly all of Robert's savings. Ong informs Joyce that Hammond's widow demands Leslie come personally to make the payoff, so Joyce arranges for the court to have her released into his custody to "regain her health".
In the Chinese quarter Leslie obtains the letter from the angry widow. She is acquitted.
In the aftermath of the trial Robert announces to Leslie and Joyce that he plans to buy a rubber plantation in Sumatra to give him and Leslie a fresh start. It will require all his savings, plus a mortgage, but he can hardly contain his excitement. Joyce informs him of the true cost of the letter, which Robert insists on reading. He is devastated to learn that Leslie had lied about the killing and had been unfaithful with Hammond for years.
As a party celebrating the acquittal gets underway, Leslie discovers a dagger on her porch which she recognizes from the shop where she retrieved the letter. Immediately aware of the implication, she nevertheless joins the party before retreating to her room to lose herself in her lacework. Robert brags to his friends about his Sumatran fantasy, but collapses in gin and misery.
Robert offers to forgive Leslie if she can swear her love to him. She does, but then abruptly confesses that she still loves Hammond.
Robert rushes from the room. Opening the door to the garden, Leslie sees the dagger is now gone. She recognizes the inevitability of her fate, and ghosts down the garden path toward it. Outside the gate, Leslie is grabbed from behind and held by her own manservant while Hammond's widow stabs her with the dagger.
The two murderers attempt to slip away, but are stopped within steps by the flashlight of a policeman, who leads them silently away.
