One day, a mysterious woman in the street grabs Monk's attention. Monk has never met the woman before but she seems strangely familiar and he feels compelled to chase her for two blocks before losing track of her. The encounter so haunts Monk that he can't sleep for days. Growing desperate, Monk takes Natalie's advice and decides to go for a late night walk, during which he sees the mystery woman for a second time. This time, the woman is driving a taxicab. Monk tries to stop her but she eludes him once again. Then, Monk hears angry voices coming from an alley. He follows the noise to a restaurant window where he sees an apparent drug bust going down. An undercover cop is pointing a gun at two men: a longhaired drug dealer and a bookish man. A fight ensues and the undercover cop is shot dead by the drug dealer. The bookish man and the drug dealer run away. Monk rushes to a pay phone and reports the crime but by the time Stottlemeyer and the police arrive on the scene, there is no body, no blood and no sigh of a struggle. Stottlemeyer thinks that Monk, in his sleep-deprived state, is seeing things and suggests that Monk go to a bar, have a drink and get some sleep.