Lois is upset that Stewie has wet the carpet in the living room. Stewie emphatically denies this, but Lois and Peter are convinced that it is a sign that Stewie is ready to potty train. However, it is actually Brian who has urinated in the house, and he tries to clean up another accident that night. The next morning he tries to discreetly put the bed sheets in the washing machine revealing that he has wet the bed. After a failed attempt by Peter at getting Stewie to use the toilet, the family goes to the supermarket to buy groceries. In the checkout line, Brian has another urination accident, revealing that Stewie (much to his own delight) is innocent.
This leads to Brian going to see Dr. Kaplan, a psychiatrist. The doctor decides Brian is having a mid-life crisis, so Brian goes traveling and exploring. Brian feels better, but shortly after returning, Stewie gets revenge and frames Brian by peeing all over the living room. Brian (who believes he has done it himself, albeit claiming he never remembered doing it) is blamed and returns to Dr. Kaplan to find out why this is still happening. After revealing that his last accident happened after watching Lois and Peter have a water fight while washing the car, Brian tells Dr. Kaplan that he is in love with Lois. Brian and Lois discuss the situation and decide to just remain friends. Peter, who is unaware that Brian's love is Lois, conjectures that Brian's beloved would "probably end up with some idiot."