An illicit physical relationship with a sister-in-law. "Just this once..." The woman's predatory instincts slip into the man's moment of weakness, causing his moral dam to burst and trapping him in an adulterous quagmire, forgetting his wife... forgetting himself... being taken. Each time they repeat this forbidden act, the two of them become addicted to the illicit pleasure. "I wish I never knew... that my wife's sister was such a slut..."
