Ain't Nobody's Business If I Do

S5, E11: When Daphne finds an engagement ring in Martin's underwear drawer, she immediately takes the shocking news to Frasier and Niles. Not aware of how serious things had become between their father and his girlfriend Sherry, Frasier and Niles try to figure out how to handle the situation. So Niles hires a detective to investigate Sherry's past.