AMERICA'S TOP TEEN DETECTIVES TEAM UP TRACK DOWN A CRIMINAL MASTERMINDNANCY DREW joins some of the best minds in the mystery field to help crack a famous unsolved case: the theft of the Comstock diamond. A private train will take the elite group from Chicago to San Francisco, the same route taken by the jewel thief fifteen years before. But someone is out to derail the search for clues and send Nancy on a chilling cross-country ride to terror.Meanwhile... FRANK AND JOE HARDY climb on board, lured by the promise of a $25,000 reward for whoever finds the diamond. Instead they find trouble: an open-air fist fight atop the speeding train, a runaway locomotive, and a beautiful gem of a different kind -- actress Kate Harkins. Joe is dazzled by her entrance -- and stunned by her exit.The teen detectives suspect she's been kidnapped, and it soon becomes clear they've all been ticketed for disaster... on the"MysteryTrain"