A wonderful house full of fascinating artifacts is not the only thing the London artist and world traveller Agatha Fynn has left to her American granddaughter Marlee, a mysterious riddle is part of the young art student's heritage too. As soon as she arrives in England, Marlee is pursued by strangers, her house is broken into, and a famous master thief is suddenly keenly interested in the paintings of her grandmother. Alone and without any friends in London, she turns to private detective Nea Fox. Together they set about to solve the mystery, but it soon becomes clear that they are not the only ones following the dangerous trail ...