Charlie Chan in Rio 1941

In Rio de Janeiro, detective Charlie Chan, [Sidney Toler], travels with his son, Jimmy Chan, [Victor Sen Yung], and the local chief of police, Chief Souto, to arrest the nightclub singer Lola Dean, [Jacqueline Dalya], whom Chan suspects of killing a man back in Honolulu. After Lola’s performance, her fiancé, Carlos, asks her to marry him, and she accepts. Her personal assistant, Helen Ashby, then reminds Lola of an appointment with a Hindu psychic, Marana, [Victor Jory]. Lola visits the psychic, who puts her in a trance-like, semi-conscious state using coffee and cigarettes laced with a special natural herb, and under this spell Lola confesses that she killed Manuel Cardozo when he refused to marry her in Honolulu. The psychic records the confession, but Lola wakes and the reader is told that the psychic will keep the conversation confidential between them.

On the way home, Lola becomes anxious about the secrecy of her confession and persuades Carlos to elope instead of a formal wedding later on. When she returns home, she begins packing to leave.

Chan, Jimmy, and Chief Souto arrive at Lola’s house to arrest her, but they are met with Lola’s body in her room. The trio quickly recognizes that Lola was murdered and that someone left deliberate clues to mislead them. They also notice Lola’s jewelry is missing. Chan informs Lola’s guests, who had come to celebrate the engagement, of the death and brings in two suspects: the psychic and Paul Wagner, [Truman Bradley]. Wagner reveals that he had been Lola’s husband, though they had separated. The psychic then plays back his recorded conversation with Lola and reveals that he is Alfredo Cardozo, the brother of the man Lola killed. Chief Souto asks everyone to stay inside the house while the murder investigation unfolds.

Later, Jimmy witnesses a whispered exchange between Rice the Butler, [Leslie Denison], and Lilly, the maid, [Iris Wong]. Rice urges Lilly to stay quiet about something she saw earlier. Chan and Souto discover scratch marks on the floor where Lola was murdered. Chan suspects the marks came from the brooch Lola wore, theorizing that a pin from that brooch would still be stuck in the murderer’s shoe. He also finds similar scratch marks under one of the chairs at the dining table where all the guests had dined. Jimmy hides in Rice’s room and uncovers Lola’s jewelry there, then brings Rice to Chan. Rice insists he has the jewels but denies killing Lola. Before he can reveal more, the lights go out and Rice is shot.

Chan gathers all the guests at their original dining-room positions and reveals the clever use of the scratch marks. He points out that the marks were under Helen Ashby’s chair. When Helen protests her innocence, Chan suggests Cardozo used the same semi-conscious treatment on her to coerce a confession. But as Cardozo attempts to admit to Lola’s murder, Helen stops him, revealing that she was the killer. She explains that she was Manuel Cardozo’s wife and learned from Lola’s conversation with Alfredo that Lola planned to elope. Realizing Lola would escape justice, Helen killed Lola. When Rice confronted her about the jewels, she had paid him to stay quiet and then shot him as well. Chief Souto arrests Helen and takes her away.

As the case closes, Jimmy asks to take Lilly back to Honolulu with him, but Chan informs him that he has already been drafted into the United States Army. The story ends with Chan’s quiet acknowledgment of a crime solved, and a reminder that justice, while slow, can untangle even a carefully laid trap.