A long running mystery series about an investment banker / amateur detective, written by Emma Lathen (a pseudonym for co-authors Mary Jane Latsis and Martha Hennisart).
The series includes examples of:
- Always Murder: Whatever irregularities the business of the book has, it produces a corpse at some point.
- Amateur Sleuth: Thatcher must solve the mystery before the Sloan can move on.
- Author Existence Failure: The death of Latsis in 1997 brought both the partnership and the series to an end.
- Comic Book Time: Thatcher is "a youthful sixty" in all books, from 1961 to 1997.
- Eureka Moment: Once per novel.
- Fair Play Whodunnit: The reader might not have all the solid evidence until after the fact, but does have all the clues that tipped Thatcher off.
- Mystery Magnet: The Sloan Guaranty Trust, "the third largest bank in the world", gets involved with a business, and some person involved with it ends up dead.
- Never Live It Down: In-universe example: His grandson received a puzzle box for Christmas; the two of them enjoyed spending the day trying to solve it. That was enough of puzzle boxes for Thatcher, but his relatives thought he was obsessed with them.
- Ostentatious Secret: Miss Corsa's tin box.
- Rich Idiot with No Day Job: Heavily averted for Thatcher himself. He is a hard worker, and expects the same of his subordinates. Played straight for bank president Bradford Withers, who appears to see his job as a collection of social contacts. On the rare occasion when Withers takes an active role, something goes wrong.
- The Summation: The books normally end between the murderer's arrest or suicide and his eventual trial, so this is how Thatcher gets the other characters (and the reader) up to date on just what was going on.