When Allison needs Gary to drive the kids to school for the next couple weeks, he can't do it because he landed a major rennovation of a historic building. Luckily, Dennis's little sister, Anna, arrives at work the next day looking for a job. Gary refers Anna over to Allison as her new full time nanny.
The next day, Anna comes over after work to Gary's to feed Lousie's fish (she didn't trust Gary to). While there, Gary offers her a beer and she shortly after tells him she's always had a crush on him and thw two start kissing. Dennis comes over and rather than being angry like Gary thought, Dennis is thrilled thinking that things might get serious between the two. Dennis would love for Anna to find a good guy and for Gary to be part of the family.
After Anna spends the morning, literally the next morning Anna is acting like they're in a serious relationship. Anna is doing laundry, packing him lunch, and cooking for him. Gary already wants out and desperately tries to get her to breeak up with him in order to keep his friendship with Dennis. When she's unwilling to dump him, he breaks up with her and is able to fix things with Dennis with the help of the other painters at work.
Meanwhile, Gary's dad has a hippie flashback at the historic home they're painting. Apparently he used to have orgies at the house back in the day. His dad manages to sleep with the woman who was doing tours of the house.