After seeing an emotional meeting between Martin and an old family friend, Frasier and Niles begin to suspect that their father had an affair when they were boys.
Niles (David Hyde Pierce) becomes convinced that Martin (John Mahoney) and an old family friend Marion Lawlor (guest star Patricia Crowly of "Please Don't Eat the Daisies") had an affair 30 years ago, and he wants Frasier (Kelsey Grammer) to join him in accusing Martin of cheating on their mother.