A mysterious little black box –– not a camera –– not a gun –– but capable of dropping a man in his tracks with no more sound than a shrill whisper can be a dangerous weapon in the hands of the wrong people as Rick Brant and his pal Scotty soon discover.

     When secret government files are invaded by a gang of raiders using the whispering box, Rick's father and the other Spindrift Island scientists set up a secret laboratory in Washington, D. C. to develop a counterweapon. Rick and Scotty know only that they are up against a new, ultrasonic invention. But it is not long before the boys have a firsthand knowledge of the whispering box, acquired during a desperate run for their lives.

     Then three of the key scientist are kidnaped by the gang. Rick and Scotty brave the whispering box again to effect a thrilling rescue, only to find that the gang leader in the meantime has gained entrance to Hartson Brant's secret laboratory itself.

     How Rick and Scotty, with the help of "Screaming Susie," finally outwit the whispering box is told in the breath-taking windup of a tensely exciting story that will keep the reader on tenderhooks to the very end.