The last time I saw "Double Indemnity," it struck me that Keyes and Walter are kind of a twisted/dark version of the Nero Wolfe/Archie Goodwin partnership, in Rex Stout's "Nero Wolfe" novels. Have you read those?

I have, and I really like the idea of Keyes and Walter as their dysfunctional reflection. (I still find Keyes more inherently adorable than I find Nero Wolfe.)