Jason Statham plays a veteran who escaped before he could be court-martialed and took to living on the streets back in England. While running from some goons who extort the homeless for rent one February night, he falls into the apartment of a photographer who is out of the country until October 1st. He takes advantage of the situation to get his life together for 9 months so he can look for a friend of his who also ran from the goons, and when she's found murdered, seek vengeance. He also sorta courts a nun who helps the homeless in the area, and tries to help his estranged wife and daughter.
It's not a happy movie. You find out late in the film what he did to be facing a court martial, it's not a case of someone being railroaded for taking a principled stand. He has bouts of PTSD, although I don't know how accurate a portrayal his hallucinations are. The money he uses to buy pizzas and takeout for the homeless guys, that he sends to his wife, that he uses to buy the nun a nice dress? Is pay for being an enforcer for a bunch of drug runners and human traffickers. He only knows how to deal with things with violence, can only hope using money he earned doing evil to help others will make up for it. Not a great long-term strategy, and he knows it.
As he puts it at one point, "they" sent him up a mountain and told him to kill, what did they think would come back down the mountain? I think that perspective informs his approach. The idea that anyone might be able to help him, or might want to, is foreign to him. He knows he's a lousy person, and dangerous, so he tries to make himself not dangerous the only way he can think of. Maybe he's right. I imagine the court martial probably sends him to prison, rather than some place equipped to help him process trauma. They either didn't think he'd come back down from the mountain at all, or they expected he'd be quietly broken, only harming himself, easily ignored.
I was left wondering at the end whether, overall, he did more harm than good during the nine months he put himself back together. Maybe on a micro level, for a couple of individuals, he helped. But on the macro level, with everything he did for that crime syndicate, probably not.