A month has passed since Eric invited Mary's ex-boyfriend to stay with them until he got on his feet. Robbie happily continues to act as a member of the household, and it's driving Annie crazy. Robbie is Eric's latest project, Ruthie's new best friend, recipient of Simon's financial advice, and according to Mary, Lucy's boyfriend. He's even cooking and folding laundry (the wrong way!). Frustrated and emotionally strained, Annie starts to think nobody needs a mother anymore. Matt also feels unneeded by the family due to Robbie, and pays an unexpected visit to Heather and her new boyfriend.

Robbie is not amused by week-long roommate Matt's jealous whining, but still helps him make up with John, who lacked the courage to tell Priscilla her 'Japanese' room remodeling disgusts both guys. Mike decides after a kiss without chemistry to trade in Lucy for Elaina Casey, while matching Lucy with Mike's friend Jeremy. Simon and Robbie prevent suddenly jealous Lucy's reactions spoiling the whole partner-switch, which thus ends well.