London, 1953.

One foggy night, in the dead of February, a diffident young man arrives unannounced at 42 Tregunter Road in Chelsea. Self-styled Bohemian Mrs Honor Wilson, who runs a minor literary journal and lodgings from this timeworn Victorian house, introduces him to her 'dear house guests': Robbie, the writer; Mina, the aspiring socialite; George, the debutante; and Saul, the refugee poet. Jimmy Sullivan is a family friend, Honor says - yet clearly, something is very amiss.

Despite everyone's suspicions, she lets the stranger move into the attic. As they each try to disprove Jimmy's dubious account of himself, secrets, jealousies, and disturbing schemes come to light, fracturing the household's delicate allegiances and setting in motion, unstoppably, a tale of perilous self-invention, complicated love, and murderous revenge.