Romola Garai wants to surprise fans with her role in Junkhearts.
The British actress, best known for her performances in period pieces like The Hour and Atonement, takes on a more contemporary role in Junkhearts, where she plays Christine - a high-flying single mother with a drug addiction.
"I've played characters with every other problem but I suppose I haven't done one like this before. Addiction is a very different thing to play - it's its own animal and instantly recognisable," she said.
"Christine is good at her job, she maintains her day-to-day life, she looks after her child to the best of her ability and she's not a terrible parent.
"She's started to run out of money but she is a drug addict - but she's able to function in a way that some people who are addicted to substances, who don't have a good support network of having a good job or a good education, aren't able to do in the same extent."
She added: "She's not on a downward spiral, she is managing an addiction that would continue indefinitely on this one substance - she's not upgrading from coke to heroin."
Romola revealed she didn't have to look too far for her research for the drama, which also stars Eddie Marsan and Tom Sturridge.
"Unfortunately, you don't need to. We all know people - journalists, actors - so you don't need to go very far," she said.
:: Junkhearts opens in cinemas on November 4.