Lady Lorraine Lister, a financer of expensive experiments, has discovered a way to obtain pure diamonds by the means of a radiation device. She hires five renowned scientists to participate in additional experiments regarding this new contrivance. However, it soon happens that the device is stolen, and the scientists mysteriously disappear! Agent Dick Smart is called in by the CIA to track down the scientists and recover the device. With the help of incredible gadgets and lots of bravado, he manages to locate the source of an underground operation in Rio De Janeiro: an operation headed by a mysterious man with a speaking device fastened to his throat..