S4, E5: Monk and Natalie are traveling to wine country to celebrate Monk and Trudy's anniversary. Every year, Monk goes to the same bed and breakfast where he and Trudy spent their honeymoon. After Monk and Natalie check in, Monk sits down to eat dinner alone, with an open seat reserved for Trudy. It’s a touching moment - until Monk is interrupted by Larry Zwibell, a loquacious guest who rudely seats himself in Trudy’s chair. After noticing that Monk is woozy after having just taken a sip of wine, Zwibell tells Monk to find him later for a great hangover cure and then leaves. The next day, Monk is indeed hung over and seeks out Zwibell for that cure. Much to his surprise, Zwibell is gone, and nobody has any recollection whatsoever of a Larry Zwibell...