In season one, none of the guys know what to think about Jess, their new female roommate, but they all seem to be attracted to her in one way or another. The guys sign a "no-nail oath", unbeknownst to Jess. Jess and Nick, two people with extremely different attitudes toward life, get along oddly well. Though the two both date various people in the first season, their undeniable attraction to one another surfaces at the season's end when Jess realizes the passion she was looking for in a relationship has existed between her and Nick all along.
When Jess is conflicted about how to date someone casually, she relies on Nick for all her emotional needs, but this eventually backfires when Nick is told that he is a boyfriend without the benefits. Jess then dates this man on and off throughout the season, but an unexpected kiss between her and Nick results in the end of that relationship. Eventually, the two go on a date, but are confused by what they want from eachother. Nick finally gains the courage to pursue Jess, but is scared off by her father the following day. The two then question whether or not a relationship would work out, but end up driving away together, agreeing that they want to be together.
Jess and Nick are forced to tell their roommates that they are dating, which comes as a shock to pretty much everyone. The two then freak out and drive away, eventually landing in Mexico, where they can be together free of judgment. However, they are forced to go back to reality and their jobs. The two continue to date back in LA, officially taking on the roles of "boyfriend/girlfriend" after some time. Their relationship continues to grow as they both admit their love for one another. After all of this, they breakup because they miss being friends. Neither of the two handle the breakup well, and the situation only gets worse when they are forced to go on a romantic cruise together.
Jess begins to date again when a handsome British teacher joins the staff at her school. The pair are smitten for eachother, but he receives a job offer in England that is too good to pass up, so the two attempt long distance. The time difference is too difficult, and Jess ends up heartbroken once again. Nick still cares about Jess, and tries to cheer her up. The two then slowly rebuild their bond as friends, but do they want something more?
The doctor who Jess casually dated in season one reappers in her life when she finds out he is dating the principal of a progressive school that she is trying to get a job at. This makes her employment situation complicated, with the doctor not agreeing to put in a good word for Jess until Nick apologizes to him for kissing Jess. The four of them end up at the shared apartment of Jess and Nick, where Nick amplifies the situation by refusing to apoligize, but somehow Nick and the doctor end up on good terms. Jess then rekindles her relationship with the doctor, and even meets his parents, but Nick is still on her mind. Nick struggles with feelings for temporary roommate Reagan, but decides to pursue a relationship with her and follows her to New Orleans for the summer.
Jess finds it difficult to be around Nick after he comes back from New Orleans because she still cares about him. Reagan moves into the loft after they need another roommate. Jess begins to date former friend Robby after a series of clumsy events leads to them spending quite a bit of time together. Jess becomes the mediator between Reagan and Nick, helping them to communicate even though she is unsure of her feelings. A shocking discovery on what was supposed to be a romantic hiking trip reveals that Jess and Robby are far too close, forcing them to breakup. She then gets a little too friendly with Nick, and forces herself to stay in Oregon, away from Nick and Reagan. Nick and Reagan struggle without Jess, and when Nick realizes that he is not getting what he needs out of the relationship, he sends Reagan packing. Jess eventually goes back, and after receiving some mixed signals from Nick, hides out at a friend's for a few days. The two eventually are forced to meet as Jess is packing up her things from the loft, and just as it happens in the movies, they get back together after a single glance.
The final season is set three years into the future. Jess and Nick are still going strong after promoting Nick's book series on a worldwide tour. The two, however, are not married. Nick ends up proposing, but superstitions the day before the wedding lead to Jess getting married in an eye patch. Following the wedding and some major life events, the group is forced to say farewell to the loft and all of the memories associated with it.