First Fitzhugh, Barry and Valerie, then Mark, Steve and Dan, are captured by Kronig, a giant industrialist who is a chess fanatic. He wants to demonstrate his superior mind against the Earthlings. To do so, he tells them to pick there best chess player to play with him. If they win, they will get there freedom.

Barry has learned trumpet playing from Dan and goes to a nightclub with Valerie and Fitzbugh. There, they see the owner, Biff, who is a lousy trumpet player and owes money to a crook, Hanley. Barry loses the trumpet and he and Valerie get captured by Biff who prepares to reluctantly turn them to the SID to make enough money to pay off his debts to Hanley.