Actress Haley Bennett was so traumatized playing a deeply damaged woman in new thriller The Girl On The Train she had to scrub herself clean in the shower every night.

The Equalizer star plays murder victim Megan Hipwell in the compelling new movie adaptation of Paula Hawkins' bestseller, and her back story of cheating is played out in the film, which also stars Emily Blunt, Justin Theroux and Luke Evans.

Haley admits playing such a dark character was tough at times.

"I wanted to play her so that she would be approachable and likeable and that was a difficult thing," Bennett tells WENN. "She was having affairs with multiple men. I didn't want her just to be a mistress or a homewrecker.

"I wanted her to be not just a monster that you don't understand why she's damaged."

But playing the character left Haley desperate to get home and wash her off after a long day on the set.

"The reality of my character was tough to shake at the end of the day," she explains. "I would go home and I would literally scrub my skin basically raw. It was the physical act of shedding her."

She wasn't the only cast member who had to completely transform for the thriller - Blunt had to play a desperate "black-out drunk".

"I just wanted it to be authentic and raw and ugly as possible," she tells WENN. "It (alcoholism) is an ugly disease and once its claws are in you the idea of a better life is an impossible one. How frightening that is. It's an ugly thing when you're around a drunk; it's not funny.

"I was nervous in portraying it, so I watched a lot of documentaries on it, 'cause rather than see other performances by actors playing alcoholics I just needed to watch the reality. (TV show) Intervention is a fantastic source that I watched on a loop and there's a documentary that Louis Theroux did (Drinking To Oblivion). I read books on depression and drinking and I know some alcoholics and I spoke to some of them either recovering or not or on the verge of wanting to recover."