Steal this idea - A cottage industry: prequels

A prequel to "The Maltese Falcon". Why didn't I think of that? To what novel (or movie) would you like to see have a prequel?

How about "The White House's Bell Tolled" where Rick (Humphrey Bogart from "Casablanca") runs guns in Spain and has a showdown with Robert Jordan (Gary Cooper from "For Whom The Bell Tolls") over Maria (Ingrid Bergman)?