The End of the Affair (Graham Greene, 1951)

This was quite different from Our Man in Havana and The Quiet American. Set mostly in WWII London; protagonist has an affair with wife of an acquaintance; various characters deal with the question of belief in God in a Catholic sort of way; this takes an unexpected turn in the latter part of the book. The private detective's son recovers; the rationalist's facial markings disappear.

I liked. Perhaps should try the movie version(s) (1955, 1999).