I’m trying to find the title of this book (spoiler)

[Paul]

Hello
I’m trying to remember the title of a book I read in an office book club February 2000. It’s a who-dunit about the murdered friend of the narrator (first person?). The body was found under a well after being missing for many years
SPOILER ALERT!!
The murderer was the narrator’s husband, Claude.
Can anyone name that book please?
Thanks in advance.
P