NYPD detective Jacob Kanon is on a tour of Europe's most gorgeous cities. But the sights aren't what draw him - he sees each museum, each cathedral, and each café through the eyes of his daughter's killer.

Kanon's daughter, Kimmy, and her fiancé were murdered while on holiday in Rome. Since then, young couples in Madrid, Salzburg, Amsterdam, Berlin, Athens and Paris have been found dead. Little connects the murders, other than a postcard sent to the local newspaper prior to each attack.

Now Kanon teams up with the Swedish reporter, Dessie Larsson, who has just received a postcard in Stockholm - and they think they know where the next victims will be.