Denzel Washington's character in 'The Equaliser' is ''troubled'' and ''flawed''.

The 59-year-old actor stars as former black ops commando Robert McCall in the upcoming action-thriller and he's explained the reason behind his character having obsessive compulsive disorder (OCD).

Quizzed on why his character was given the ailment, he revealed: ''We added it so he's not just the action guy. He's troubled, flawed and we don't finish the story - it's not like suddenly at the end he's fine.

''It's been an interesting development as we've gone along. We started talking about it and adding things, opening doors five times. We obviously did a lot of research about it.''

Washington's character is a man who believes he's put his mysterious past behind him after faking his own death until he meets a young girl named Teri, played by Chloe Moretz, who is under the control of ultra-violent Russian gangsters.

Armed with hidden skills, he comes out of his self-imposed retirement and finds his desire for justice reawakened as he attempts to rescue his new acquaintance.

Speaking about his character's turmoil at choosing to return to fighting crime, the 'Man on Fire' star told Screen Rant: ''Well, I think he's looking to put his past behind him ... He's trying real hard.

''I actually say - there's a line I say, 'I've done a lot of bad things in the past, things I'm not proud of'.

''I actually promised - in my back story, I promised my wife that I wouldn't go back to being that person, but you wouldn't have a movie then, so he's drawn back in.''

'The Equaliser' is scheduled for release in September.