It's Randy's birthday and when Natalie's date can't make it to her brother's wedding, she agrees to let Randy accompany her.  When he is run down in the parking lot outside the hotel, Monk and Stottlemeyer go undercover to the wedding to find out who was behind it.  The bride-to-be Theresa turns out to be a suspect in a case Randy was investigating years earlier in which she murdered her new husband for his money.  Before the bride and groom can leave, Randy is able to identify her and Natalie and her mother finally make amends.