A wealthy playboy and his wife hire a great white hunter to guide them to the African hunting grounds.

A plane lands in Nairobi, Africa, carrying Margo Macomber, white hunter Robert Wilson, his African guides, and the dead body of Margo's husband, Francis. Police Captain Smollett asks Robert to fill out a homicide report, even though Robert insists that Francis' death--by a gunshot in the back--was an accident. Robert writes "accident" under Cause of Death in the report, but then throws it away, remembering the day he first met the Macombers: Francis, an excitable, boyish and wealthy American, who is hoping to prove his courage, hires Robert to take him hunting. Margo, whose marriage to Francis has deteriorated, is immediately taken with Robert's manly beauty and courage, and is unrelenting in her criticisms of her husband. The first night in camp, as Margo pretends to sleep, Francis promises her that, although they have quarrelled in the past, he has fallen in love with her again and wants to start over, but she does not respond. In the night, Francis is awakened by the roar of a lion a mile from camp, and in the morning, is determined to kill it. During the hunt, Francis shoots the lion, sending it into the brush to lick its wounds. Although Francis is afraid to complete the kill, Robert insists that a hunter cannot leave an animal to suffer, and leads Francis into the brush. When the lion charges, Francis runs, leaving Robert to kill the lion. Margo, furious at Francis' cowardice, greets him after the hunt with hostility, but kisses Robert on the lips in front of her husband. Later, Francis, feeling sorry for himself, beats an African servant, and Robert must intervene. The incident deepens Margo's animosity toward Francis, and that night, she visits Robert as Francis sleeps. He awakens, however, and finds her missing. The next day, Francis becomes exhilarated before the hunt. Although Margo tells him she hates him, he finds his courage at last and successfully shoots a buffalo. Robert congratulates Francis, then admits he is in love with Margo. After Francis and Robert shake hands, a wounded bull charges out of the brush in Margo's line of fire, and she shoots Francis in the back, killing him. Back in the present, Robert confronts Margo, who is scheduled to appear before a jury. She admits that, after years of tolerating Francis's cowardly brutality toward those weaker than he, she grew to hate him and became callous and cold. After she saw Francis and Robert shaking hands during the hunt, she knew that Francis was through with her. Finally, she confesses that if there is such a thing as "murder in the heart," then she murdered her husband. Robert then admits that he already noted in the police report that Francis' death was an accident, but forced her to confess so that he would know what kind of woman she is. Although Robert offers his support, Margo leaves to face the jury alone.