A detective travels south of the border to investigate an art dealer's murder.
Tom Lawrence AKA The Falcon (Tom Conway) encounters a young woman hiding in a doorway. Her name is Dolores Ybarra (Cecilia Callejo) and she asks The Falcon to help her retrieve a stolen painting from a nearby art gallery. After breaking into the gallery Tom realises that Dolores was the model for the portrait not the artist and then stumbles upon the dead body of the gallery owner. Alerted by a burglar alarm, security guards arrive. When Tom explains to them what happened they do not believe his story as Dolores has vanished. The guards reveal that the portrait was painted by Humphrey Wade who has been dead for 15 years and so could not have employed the youthful Dolores to be the model. When the guards try to arrest Tom, he escapes with the painting and takes it to the home of Winthrop "Lucky Diamond" Hughes. Hughes (Emory Parnell), who is known as "lucky diamond" due to an enormous diamond ring he wears, is a noted collector of Wade's work and he quickly identifies the portrait as being a genuine work by Wade.
Hughes suggests that Tom should go and question Wade's daughter Barbara about the painting, but when Tom goes to her apartment there is no answer at the door. The Falcon breaks into the apartment, where he finds a stack of newspaper clippings about the sale of Dolores' portrait. When Barbara Wade (Martha Vickers) returns home Tom asks her about the painting and she tells him that she believes that her father is not dead. The police, who have been alerted by Hughes, arrive prompting Tom to plan to go to Mexico (where Wade is said to be buried) and Barbara insists on going with him. After giving the police the slip the pair fly out to Mexico City but at the airport Barbara gives The Falcon the slip and is met by a car from the La Casa Del Laga Inn. Tom hires the taxi of Manuel Romero (Nestor Paiva) and his son Pancho (Fernando Alvarado) to follow her. They track her to the Inn, which is located in a small rural village. There Tom confronts Barbara and she explains that she has come to the Inn because that is where he father lived and worked. She introduces him to her stepmother Raquel (Mona Maris) and her dance partner and new husband Anton (Joseph Vitale). Anton warns Tom to leave Barbara alone and leave Mexico. The following morning Raquel asks Tom to abandon his search for Wade, but Tom accuses her of trying to curtail his investigation for fear that she should be judged a bigamist if Wade were indeed found to still be alive.
Back at the Inn, the desk clerk, Paula Dudley (Mary Currier) shows Barbara and Tom to Wade's studio which she has kept just as the artist left it. As Barbara is leaving the studio she suddenly senses the presence of her father behind a locked door and Tom picks the lock. Inside the room they find a painting done in Wade's style and the paint is still wet, Paula arrives and orders them out of her room. When asked about the painting Paula claims it is her own work, but Tom suggests that she is in fact creating forgeries of Wade's work. Returning to his own room Tom startles Dolores who is searching for her portrait, Tom goes after her into the hallway but she has gone. The Falcon returns to his own room and is just about to retrieve the painting when a man knocks him out and steals the portrait. When he comes round Tom questions Paula about Dolores and she tells him that she is the daughter of Don Carlos Ybarra (Pedro de Cordoba). Tom goes to visit the Don and informs him that his daughter may be in danger, the old man tells Tom that Dolores travelled to the United States to assist an artist friend recover a painting. The Don and Tom search for Dolores, but they are too late - her body has been found drowned in the lake.
Tom returns to the Inn only to find Manuel rummaging through his belongings and fires him. Soon after, Hughes arrives at the Inn but without his famous ring. At dinner that evening Barbara collapses at the table, she has been poisoned. Tom concludes that whoever poisoned her also drowned Dolores and murdered the art dealer back in New York all to prevent it being discovered if Wade is really alive. Paula remarks that Raquel has a strong motive for ensuring that Wade remains dead, which prompts Anton to accuse her of killing the art dealer because he had recognised her paintings as forgeries of Wade's work. When Barbara has recovered from the poisoning attempt, Paula disappears and when Tom goes to he room he finds the missing portrait hidden in her desk. When Tom goes to the lake to look for Paula he discovers her dead body in a boat but as he approaches the boat Manuel appears and reveals that he is in fact an undercover Mexican police officer.
Barbara is at the village plaza when a local woman approaches her and tells her that she will lead her to her father. When Tom and Manuel return to the Inn and discover that Barbara is missing they follow her to an island where her father's grave is located. Tom removes the headstone of the tomb and they find that the crypt is empty, this prompts the woman who led Barbara there to admit that Anton had paid her to bring Wade's daughter to his tomb. The local villagers are holding a fiesta and the local police report to Manuel that one of the traditional dancers scheduled to take part in the fiesta has had their costume stolen. When Tom hears that the costume is that of an old man, he deduces that Wade has stolen it so that he can disguise himself. Tom and Manuel go with the police officers to question the dancers, but almost as soon as they have gone a man wearing a costume and mask approaches Barbara and lifts his mask to reveal that it is Wade (Bryant Washburn). He explains to his daughter that he disappeared because his life was a failure, but after his alleged suicide his paintings suddenly became valuable meaning that he could not even let her know that he was actually still alive. He goes on to warn Barbara that both of their lives are now in danger, but barely have the words left his lips than he is shot in the back and killed.
Hearing the gunshot Tom goes to Barbara and when he sees her dead father concludes that it is Hughes who is the killer as his collection of Wade paintings would be rendered virtually worthless if it proven that the artist was still alive. Manuel confirms that Hughes is in financial trouble and has even had to sell his lucky diamond ring prompting The Falcon to come up with a daring plan to lure Hughes out into the open. Tom dons the old man costume Wade was wearing and walks conspicuously out into the middle of the plaza. Thinking his attempt upon the life of the artist has failed Hughes takes aim from a balcony, but before he can fire Manuel spots him and shoots him dead. With the case solved The Falcon says goodbye to his friends in Mexico and boards a plane for New York.