Look at the Old Man Go

Mike is hired by a beautiful heiress to break up her father's romance with a much younger woman. Mike goes to the woman's apartment and, after interviewing her, decides it really is a May-December romance and determines to give up on the assignment. When a thug claiming to be Mike Hammer threatens the lovely lovebird with bodily harm if she doesn't give up her sugar daddy, Mike gets back on the case and investigates who would really benefit if the romance were scotched.