Fourteen-year-old twins Joanna and Samuel Clark of London, England, were invited to join their friend Gareth Morgan and his parents for what promised to be a fun, weeklong vacation in New York City. But no sooner have they embarked on their first sightseeing tour than the twins find themselves being chased through Penn Station by four mysterious men. Narrowly escaping their pursuers, Joanna and Samuel happily reunite with Gareth, only to be swept...