In the thrilling mystery-comedy, Blanche Tyler (Barbara Harris), a fake psychic, joins forces with her boyfriend George Lumley (Bruce Dern), to track down the long-lost nephew of the wealthy and sorrowful Julia Rainbird (Cathleen Nesbitt). Julia wishes to make the boy her heir, offering $10,000 for his return. However, little information exists about him, as he was given up for adoption by Julia's deceased sister.
During their investigation, George discovers the boy was named Edward Shoebridge, who allegedly died in his youth. As he digs deeper, he finds a connection to Joseph Maloney (Ed Lauter), a man who paid for Edward's gravestone long after the child's expected death, leading George to suspect that the grave could be empty. While George's sleuthing skills rival Blanche's psychic abilities, their relationship endures the test of frustration and banter as they navigate this complex case.
Unbeknownst to them, Edward has reinvented himself as Arthur Adamson (William Devane), a successful jeweler in San Francisco. He is now the mastermind behind a series of high-profile kidnappings, along with his girlfriend Fran (Karen Black). The couple confines their wealthy captives in a hidden room beneath their home, demanding large ransoms in rare jewels, with Arthur cleverly concealing their latest ransom—a magnificent diamond—right in the glare of a chandelier.
When Arthur learns of George's inquiries, he turns to Maloney for help in eliminating both George and Blanche. Maloney initially hesitates but ultimately sets a trap, sabotaging Blanche's car, leading to a near-fatal crash. The chaos escalates when Maloney meets his demise in an explosive accident while trying to escape the scene.
At Maloney's funeral, revelations unfold as his wife, Mrs. Maloney (Katherine Helmond), succumbs to George's questioning and reveals that Edward has transformed into Arthur Adamson. As George works his night shift as a taxi driver, Blanche embarks on her own quest to find the elusive Arthur. Utilizing her wit, she overhears the son of a kidnapped bishop and cleverly extracts Arthur's home address from his unsuspecting assistant Mrs. Clay (Edith Atwater).
Now caught in a pivotal moment, Blanche confronts Arthur and Fran at their residence but is soon taken hostage as she discovers the bishop beaten unconscious. Meanwhile, George, sensing the danger, meticulously searches Arthur's house for any sign of Blanche. After an intense confrontation, they devise a plan during her staged unconsciousness to turn the tables on their captors.
As tension mounts, Blanche, seemingly in a trance, unexpectedly reveals the diamond’s hiding place, leading George to realize that she might indeed possess real psychic abilities. With a sense of urgency, he calls the police to aid in capturing the kidnappers and securing the stolen jewels. In a final twist, Blanche winks at the camera, leaving the audience with a mix of anticipation and amusement.
