The two actors discuss the joys of working together and getting into character
Credit: Erika Goldring/Getty Images for Screen Gems

When 21-year-old actress Jaz Sinclair got the news that she will be acting alongside Morris Chestnut for her first big movie role, she was excited and grateful to be working with one of her idols.

“I was so excited like I’m a Morris Chestnut fan and now I’m an even bigger fan having worked with him,” Sinclair tells PEOPLE at Essence Fest. “Just working with someone who’s so talented and who’s been in it for a while and just such a kind person. There’s nobody I would have rather done it with.”

The two are starring in the upcoming drama When The Bough Breaks about a couple, John and Laura Taylor [Morris Chestnut and Regina Hall], who hire a surrogate, Anna [Sinclair], who becomes obsessed with the father-to-be.

Chestnut, 47, says he was also honored to work with the young Paper Towns actress.

“I was looking forward to seeing the actress we were gonna be able to get because it was an extremely challenging part for an actress of that age,” Chestnut tells PEOPLE at Essence Fest. “You can’t fake a role like this. You can’t because it’s glaring and when someone does it as great as Jaz did it, you know she was in those moments.”

However, Sinclair did not have an easy job with playing a dangerous, seductive surrogate. She says she had to visit surrogate agencies and research foster care children in order to relate to her character’s emotions.

Her co-star also had to do some prepping for his role. Although the Best Man star has had plenty of practice with emotional roles over the years, he says he still finds it challenging to dig into his personal feelings to translate them on-screen.

“We pull things from our past experiences and certain things that you suppress living life. It can be therapeutic,” Chestnut says. “It gets really tough. It can be emotionally exhausting but it’s good.”

The thriller is scheduled to be in theaters September 16, 2016. “I can’t wait for people to see it. It’s incredible,” Chestnut tells PEOPLE.