And Then There Were 58: The Seven Dials Mystery by Agatha Christie

Join us as we frantically dig our way out of the grand old estate
of Chimneys (last visited in The Secret of), like cartoon convicts
shoveling our way to freedom.... This is the last of the early
Christie thrillers, and if you haven't had your fill of secret
societies, happily-ever-afters, or clock masks, you're in luck.
There are actually some bright spots here; this may be Christie's
most Wodehouse-ian novel yet.