My Lover's Lover by Maggie O'Farrell

When Lily slips on the sidewalk outside a London gallery and literally falls at the feet of a stranger, Marcus, the attraction is instant and electric. Within a week she is sharing this magnetic yet elusive architect's waterfront loft and sleeping in the room that belonged to his girlfriend, Sinead, about whom he will only say that "she's no longer . . . with us." But there lingers a distinct presence, of a woman who seems to have disappeared abruptly--leaving behind a single sexy dress in the closet, a puzzling mark on the wall, and the suffocating scent of jasmine. As Lily falls ever more deeply in love with Marcus, Sinead's aura consumes her with fear and obsession that spark a drama of passion and betrayal