Mix Cellini (which he pronounces with an S rather than a C) is superstitious about the number 13 and has always felt dogged by ill-luck. In the house where he lives, there are 13 steps down to the landing below his rooms. His landlady lives her life almost exclusively through her library, blind to the neglect and decay around her.
However, Mix is obsessed with the life of the notorious John Christie, who lived in the same Notting Hill neighbourhood at 10 Rillington Place. He is also infatuated with a beautiful woman who lives near-by, a model who wouldn't look twice at him. Both landlady and lodger are caught up in their own psychologically twisted parallel worlds. But when reality intrudes into Mix's life, a long pent-up violence explodes.