Why is the ghost of a distressed woman running through a corridor in the Paris metro? Kay, a translator, finds herself being drawn into a puzzling web involving two gifted musicians, a maker of beautiful jewellery and a morose but attractive bookseller with a passion for poetry, who may have caused his wife's death. Key to the mystery is the fate of a missing black cat. The story of secrets and betrayals unfolds against the backdrop of present-day Paris, with its boulevards and cafes, tiny flats in old buildings, bridges over the Seine, and not least the dark underground maze of tunnels and corridors that make up the metro. Should limits be set to love? And what are the consequences of sexual jealousy? They will all find out - except, perhaps, the cat.