Just like the rest of us, Justin Hartley gets emotional while talking about This Is Us.

In Season 1, Hartley's character, Kevin Pearson, seemed to be the only Pearson who had fully recovered from Jack's (Milo Ventimilgia) tragic death. But as Season 2 began, fans saw the true depth of Kevin's pain as it spiraled into drug abuse, alcoholism and deep depression. In a shocking turn, Kevin found himself breaking down outside of a hook up's house at his lowest moment of the series. Hartley sat down with TV Guide for our Best Performances series to talk about his heart-wrenching performance in "Number One", and readers be warned — it's an emotional roller coaster.

"We see him hit rock bottom," says Hartley of Kevin. Unable to get more prescription meds to which he became addicted after re-injuring the knee that cost him his football scholarship, he shows up drunk to his high school reunion, where he's being honored with an award. Standing in a room full of people who only see him as a success story, as a man who became a famous actor in spite of a traumatic football injury and the death of his father, Hartley says that Kevin feels more isolated and helpless than ever.

"Kevin is this guy that's kind of in a crowded room and he's completely alone," says Hartley. "I saw him as searching so hard to find answers and open to listening but no one was willing to accept that this guy actually needed help."

The only person who tries to reach out to Kevin at the reunion is Charlotte, a woman he'd never noticed in high school. Charlotte tells Kevin she's always had a crush on him, and after finding out she's a doctor, Kevin ends up back on the football field with her. In a crushing monologue, Kevin relives his second greatest high school failure, except this time, he isn't injured and Jack is smiling proudly from the stands as Kevin's future unfolds the way it should have.

"I remember getting myself in a place mentally of, what if this guy could have one more convo with his dad," says Hartley. "I believe if Jack was there, if he could have one more conversation that lasted more than 10 seconds, he could probably make it all better. That space in between what it could have been and should have been and what it is, is where I operated. I didn't look at it as me just talking to no one, I looked at it as [Kevin] talking to one very specific person."

The monologue became the catalyst for Kevin's ultimate breakdown at the end of the episode. He goes home with Charlotte, not because he's interested in her, but on the off chance that she keeps a prescription pad at home from which he can steal a leaf. Lulling her into thinking he would stay the night, he ransacks her bedroom while she's fixing a snack in the kitchen and sneaks out the door once he finds what he's looking for. The tables turn on Kevin quickly, however, when standing in line at the pharmacy with a forged prescription, he realizes the only memento he has of his father, a medallion he never takes off, isn't on him. It's somewhere on Charlotte's bedroom floor. Returning to the scene of the crime, Kevin breaks down outside of her house after she rightfully refuses his pleas to be allowed back inside to search for it. At this point, there's no amount of self-medication that can help him.

"It's about the pain," says Hartley, whose thrilling performance is likely to earn him an Emmy nod for Best Drama Supporting Actor. "The major reason I think this episode is so important is that there are people out there, really good people, that are going through this real difficult thing: drug addiction, mental illness depression. This was something that was something that was sort of bigger than the show, I wanted it to be real and honest."

This Is Us is now streaming on Hulu. Nominations for the 70th Annual Primetime Emmy Awards will be announced July 12 with the ceremony airing Monday, Sept. 17 on NBC.