Grace Latham is our narrator, and she describes San Joaquin Terrace in 1942 San Francisco. The city is on edge, and there are frequent blackouts to prevent bombing by the Japanese. The story centers on philanthropist Loring Kimball, his second wife Lucy, daughter Thorne and stepdaughter Amelia. Kimball is seen as an eccentric, having moved his Victorian home up the hill to its present location, next to architect Prentiss Vale'. He keeps his first wife's bedroom as a shrine, locked, with the lights on all night. This has become a concern as the wardens have to get the light turned off during blackouts.

Neighbor Nat Donahue is employed by Kimball, who controls him by holding a number of financial notes owed by Donahue. Although married to Ilya, Nat is in love with Kimball's daughter, Thorne; their marriage having been denied by Kimball.

Kimball is working in his study one night, as the air raid siren goes off. All the lights in the neighborhood go out, and when the All Clear sounds, he is found dead at his desk. An autopsy reveals poisoning by cyanide. Latham teams up with Capt. Primrose to investigate. RM