It should have been a wonderful holiday: four young people travelling together through the Italian countryside to Venice. Everyone is so friendly - particularly the charming elderly gentleman who shares his first-class railway carriage with them for part of the way. So it is a terrible shock, on their arrival at Turin, to discover that Signor Galassi has been the victim of a brutal attack - a sordid little robbery with violence.

Their spirits somewhat dampened, the four continue on their journey, only to find that trouble pursues them. For they have inadvertently walked off with crucial evidence of a more serious crime - evidence that someone needs desperately to retrieve....