[1] The novel is set after World War II, but in its first chapters this seems like a mere frame story, with Wimsey recounting to his wife Harriet the reminiscences of the start of his detecting career in 1921.

As a shell-shocked veteran of the First World War, the young Wimsey had been invited to an engagement party at the house of the Attenburys, another aristocratic family.

He was present when an emerald family heirloom disappeared, and discovered in himself a talent for detection—leading to the discovery of the missing stone (and incidentally saving his friends' daughter from marrying a rogue).

This was the Wimsey family's original medieval residence which had been covered up, incorporated into the later structure, and forgotten for centuries, but which at the critical moment has saved the house's east wing from the fire, including the library with its priceless old books.

Reviewer Margaret Copsewood suggested that losing 16th, 17th and 18th century additions and having to make do with the original Norman structure can be read as a metaphor for Britons having to adjust to the loss of their centuries-old Empire — a process taking place in the period in which the book is set [2]