Jimmy Shive-Overly (Chris Geere) left Gretchen (Aya Cash) — and fans — heartbroken when he ran away immediately after proposing to her in the You're the Worst Season 3 finale. And after three months without contact from her ex-fiancé, Gretchen is (understandably) bearing serious resentment towards Jimmy when he resurfaces in her life this season.

"I don't know if anyone has seen the movie The Grudge -- I have not — but I feel like it might be a good reference point for Gretchen's revenge," Cash tells TV Guide. "Gretchen just gets weird. She does some weird stuff with Jimmy. I say it's creative revenge."

Adds Geere: "The revenge is far worse than I think any of the audience could ever imagine. She goes bonkers."

During their time apart, Gretchen and Jimmy both do everything they can to hide from their problems, with Jimmy living in a retirement mobile home community and Gretchen becoming a hermit and even smoking crack. But eventually, Jimmy will return to L.A. and attempt to fix his relationship with Gretchen in his own unique and troubled way.

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"It's really tricky for these two characters to take responsibility for their actions in any way. It's going to take them a long time to recognize that they need to change in order to progress," Geere says. "He constantly says something or does something which sets him back a couple of weeks."

Despite Jimmy's often backwards way of apologizing to Gretchen, Geere insists that the notorious narcissist is willing to put in the work to try and make things right. "I think he wants to put in a lot of work to mend this relationship," the actor says. "How he's going to do it, the application of how he's mending it, will take a long time, but the intention is there."

Meanwhile, You're the Worst creator Stephen Falk teases that Jimmy will attempt to distract himself from his guilt and how much his misses Gretchen in a variety of ways. "There will be a big hole that he'll be trying to fill, both with the success of his new book and then other women and obviously alcohol, which is always there for him," Falk says. "But he's on a trajectory back to her. I just think it'll take some figuring out how and what that looks like."

You're the Worst premieres Wednesday, Sept. 6 at 10/9c on FXX.