When a minor European leader is assassinated, Solo steals a medallion from his body containing a microdot listing the THRUSH agents in the country, but must elude the secret police and outwit intelligence agent Satine (Ricardo Montalban), who also wants the medal. Teacher and tour guide Sara Taub (June Lockhart) and her high school students are used by Solo to try and sneak the medal over the border.

Solo and Illya discover that the world diamond market is being affected by a gang of English criminals headed by Blodgett, who smuggle diamonds inside pudding sold unwittingly by Victoria Poque. They enlist the aid of a master diamond thief, Rafael Delgado. Solo and Victoria end up in Brazil, with Solo tied to the front of a cannon and about to be executed.