A Mysterious Woman is ruining Barney's mojo by warning women to stay away from him. Only Lily has seen her, but before she'll help him identify the woman, Lily forces Barney to go back and confront the girls who are most deserving of an apology. Using the NCAA tournament bracketology the gang takes the top sixty-four women Barney has been with and narrows the list down to The Final Four; the four women Barney must apologize to and face the repercussions.