The first person narrator is Charles Hayward who, towards the end of the Second World War, occupies some post in Cairo. There he meets Sophia Leonides, a smart, successful young Englishwoman who works for the Foreign Office. They fall in love, but put off getting engaged until after the end of the war when they will be reunited in England. Hayward returns home only to find an obituary in The Times: Sophia's grandfather, the wealthy entrepreneur Aristide Leonides, has died, aged 85. Due to the war, the whole family has been living with him in a sumptuous but ill-proportioned house called "Three Gables"–the 'crooked house' of the title. When the autopsy reveals that Aristide Leonides has been poisoned with his own eserine-based eye medicine via an insulin injection, Sophia tells Charles that she can't marry him until the matter is cleared up.