Raymond Chandler's third Philip Marlowe mystery. There are a pile of Chandleresque gems here, but here's one I especially liked:
From thirty feet away she looked like a lot of class. From ten feet away she looked like something made up to be seen from thirty feet away.
Marlowe is summoned to Pasadena by Mrs. Elizabeth Bright Murdock, a domineering dowager with a fondness for port. She's discovered that one of the valuable coins left to her by her (second) husband, the "Brasher Doubloon" is missing. She strongly suspects her daughter-in-law, Linda Murdock (née Conquest), who has seemingly vanished after a spat with ne'er-do-well son, Leslie Murdock. Linda used to be a roomie with entertainer Lois Magic.
And, yes, that's a lot of characters with initials "L. M." Surely that's not mere coincidence? Why does Mrs. Murdock's secretary, Merle, have a handkerchief with those very initials handy? And why does Merle seem to be just a few minutes away from a nervous breakdown? Leslie, it turns out, is deep in debt to a shady nightclub owner. And Marlowe is being clumsily tailed by a young man in a coupe. An eccentric coin dealer is interviewed. And…
And things get even more complex from there. Marlowe eventually unknots the tangled plot threads, and eventually we learn why that High Window in the book title is kind of important.