A wealthy lord dies and is entombed with a valuable deposit of jewels. Seven keys are required to unlock the tomb and get hold of the treasure. A series of mysterious events causes the keys to be scattered, and when trying to unravel the circumstances, the heiress of the fortune and her companion investigators become entangled in a web of fraud, deceit, torture, and murder.
It becomes obvious that family physician, Dr. Manetta, is the untrustworthy person. Assisted by the mute family
butler and the family chauffeur (a forger on the run), Manetta seeks to steal the treasure for himself. When rightful heiress June Lansdowne arrives, she is seized and locked in the tomb before she can announce her presence. She is eventually freed by a pet monkey that steals the key to the tomb.
Suspicion grows when Dr. Manetta announces he is an admirer of Torquemada (the chief torturer during the Spanish Inquisition); and that he keeps a museum of torture instruments in the basement.
When the authorities close in, Manetta is trapped in an automatic spiked mummy case. The police reluctantly rescue him. Manetta makes a full confession, then commits suicide by poison. He is proud that he killed himself with a goblet once owned by Lucretia Borgia.
The treasure is discovered inside the tomb, the one place Manetta didn't search because he didn't want to call attention to Lansdowne's captivity there.
