In the upcoming episode of HBO's "The Leftovers," titled "A Most Powerful Adversary," Kevin Garvey (Justin Theroux) spirals out of control, and Nora (Carrie Coon) disappears.

The synopsis posted by TV Guide for Episode 7 of Season 2 reads, "Nora delivers shocking news to Jill (Margaret Qualley) and Kevin, who worries about how to solve his Patti (Ann Dowd) problem. Meanwhile, Jill goes on an adventure that couldn't happen anywhere else; and Laurie (Amy Brenneman) makes a decision that affects her whole family."

In Episode 6, Kevin revealed to Nora that he believes that he is going crazy. He sees and talks to Patti, the cult leader who took her own life in Season 1.

However, Nora had her own issues to deal with, after discovering that she may be a Lens, an energy-exuding person responsible for the departure of others. Though she fears being alone, she decides that she has to leave.

According to a teaser for Episode 7, Kevin isn't aware of this, only learning of her disappearance when he wakes up handcuffed to a bed with only Patti to talk to.

No one around Kevin has noticed his deteriorating mental health this season, and in the upcoming episode, it just gets worse. Kevin begins to sleepwalk, and can't remember where he has been or what he has done.

While Kevin looks for Nora, he will also finally challenge Patti. In the clip, he asks her what she wants.

Patti responds, "I'm glad you finally ask, Kevin."

In a pivotal scene, Kevin calls out to Patti, ready to face her, while standing in the middle of the woods. She appears.

"You think I'm scared to do battle with you," she says. "I am so very ready to do battle."

Check out the preview below and watch Episode 7 of Season 2 of "The Leftovers" on Sunday Nov. 15 at 11:30 p.m. on HBO.