Charlie Chan in Rio

Lola killed Manuel Cardozo after he refused to marry her. The psychic session revealed that Manuel had jilted Lola, and in her anger and desperation, she murdered him. This crime is what Charlie Chan was investigating when he traveled to Rio.

The motive is revealed during Lola's trance confession to the psychic, which serves as the initial key to the case.

The psychic Marana placed Lola in a semi-conscious trance using coffee and cigarettes laced with a special natural herb. In this vulnerable state, Lola confessed to killing Manuel Cardozo. The psychic recorded the confession, though Lola had no memory of revealing this information when she awoke.

The use of the herbed cigarettes and coffee creates the initial breakthrough in the investigation.

Helen Ashby was actually the wife of Manuel Cardozo, the man Lola murdered in Honolulu. When Helen heard Lola's confession during the psychic session, she learned that Lola planned to elope and escape justice. Realizing Lola would never face consequences for killing her husband, Helen killed Lola to avenge Manuel and prevent her escape.

Helen's presence at the psychic session and her later resistance to the investigation hint at her personal stake.

Charlie Chan discovered scratch marks on the floor where Lola was murdered and under a chair at the dining table. He deduced the marks came from a brooch Lola was wearing, and that a pin from the brooch likely remained stuck in the murderer's shoe. The marks under Helen Ashby's chair ultimately revealed her as the killer.

Chan methodically connects the floor scratches to the positioning of guests at dinner, narrowing down the suspect list.

The Hindu psychic Marana was actually Alfredo Cardozo, the brother of Manuel Cardozo (the man Lola murdered in Honolulu). He posed as a psychic to get close to Lola and trick her into confessing to his brother's murder. He recorded her confession but kept it confidential, intending to use it in his own way.

Alfredo's true identity is revealed after he plays back the recorded confession to the assembled guests.

Rice the butler was killed during the investigation. After Jimmy discovered Lola's missing jewelry in Rice's room, Rice was confronted but insisted he didn't kill Lola. While being questioned, the lights went out and Rice was shot. Helen Ashby later admitted to paying Rice to keep quiet about what he saw and then shooting him when he threatened to reveal too much.

Jimmy's discovery of the jewelry in Rice's room sets the stage for the butler's tragic end.

After her psychic session where she unknowingly confessed to murder, Lola became anxious about her confession being discovered. To escape the consequences, she convinced Carlos to elope immediately rather than wait for a formal wedding, planning to flee Rio before the police could arrest her.

Lola's sudden change from accepting Carlos's proposal to insisting on elopement signals her panic about the confession.

Helen Ashby was the wife of Manuel Cardozo, the man Lola murdered in Honolulu. This personal connection is why Helen was so desperate to ensure Lola faced justice. When she learned from the psychic session that Lola planned to elope and escape punishment, Helen took matters into her own hands.

Helen's unusual interest in the psychic session and her later desperation to stop the investigation become clear with this revelation.

Helen paid Rice with Lola's stolen jewelry to keep him quiet about what he had witnessed. Rice had seen something incriminating related to Lola's murder, and Helen needed to ensure his silence to protect herself. However, when Rice later threatened to talk anyway, Helen killed him to prevent exposure.

The jewelry found in Rice's room provides the financial motive for his attempted cover-up.

Charlie Chan traveled to Rio de Janeiro because he had sufficient evidence to suspect Lola Dean of murdering Manuel Cardozo in Honolulu. Chan wanted to bring her back to face justice for the crime, arriving with local Chief Souto and his son Jimmy to make the arrest.

The trip to Rio establishes the initial premise of the investigation.