The Mathnetters receive a call in regards to a kidnapping. Hans Balpeen has mysteriously gone missing, and his wife Beulah has found a ransom note from the kidnappers demanding not money, but some of Mr. Balpeen's "special skills", which are unspecified. Later on, Kate and George soon receive another call even more bizarre: millionaire Orson Kane has discovered, on his front lawn, a huge wooden hamburger. Arrangements are made for the hamburger to be moved inside Mr. Kane's mansion. The next day, however, Kate and George receive word about a robbery; the world famous Despair Diamond has been stolen, in spite of there being heavy surveillance at the mansion. After George discovers hinges on the wooden burger, it is assumed that the thief used the burger as means to get in undetected. Meanwhile, Hans Balpeen is still missing. It is learned that his special skills include plumbing, hang gliding and performing as a clown. Further investigation offers the idea that the thief may have escaped by sailing away in a helium balloon, which is found in the park by police. The case takes a sudden turn when Hans suddenly returns, unharmed. Kate and George meet with Hans at his home where he describes his ordeal. He explains that he was taken to a shack in the woods were he was forced to cut a valuable diamond into seven pieces, and was later dropped off somewhere in the mountains. He then found a road and hitchhiked home. Kate and George are happy that Hans is safe, but are forced to give Mr. Kane the painful news that his diamond is destroyed. They begin to discover clues relevant to the case, however. Beulah Balpeen had displayed some helium filled party balloons in the kitchen. The cowboy boots that Kate had noticed Hans wearing were brand new, and therefore couldn't have yet been worn in the mountains. George also points out that the kidnapping took place before the diamond was stolen, and logically should have happened the other way around. They now suspect the kidnapping may have been staged. Kate and George return to the Balpeen residence as Hans, in his clown gear, is preparing for a party. Beulah serves coffee, and moments later, George notices his half full cup completely full. He discards the coffee, revealing the Despair Diamond, uncut and still in one piece. Hans is put under arrest for theft, and the diamond is returned to a relieved Mr. Kane.