A notorious jewel thief named Justin arrives in town at the same time as a shipment of famous jewels arrives for display in a local museum. Ironside must keep the thief guessing about the method of shipment so that the jewels will remain safe; but he is up against a mastermind and there is still an inside man who has to be unmasked.

Taking an important witness from Hawaii to San Francisco by plane, Ironside discovers that a fellow passenger is a hitman. He has to find out who is trying to kill his witness before the plane lands; but there may be more than one person trying to claim the reward for an open contract.