We don’t know how old Rose (Andrea Riseborough) is, but we know she’s too young to marry without the permission of her parents. 15? 16? Young enough to be impossibly stupid. Young enough not to know better than to set awful, self-destructive patterns in her relationships with men. Of course she’s the sucker in Rowan Joffe’s Brighton Rock.

Those glasses, that mass of hair, those little fingers, that drab coat — Rose is accustomed to being invisible. Or worse: frozen out by the other girls at Snow’s, that tea shop on the boardwalk that pretends at gentility. The only kind of attention she gets is unwanted, like when hapless Freddie Hale (Sean Harris) tries to use her as a shield as the rival gang members descend on him to make him pay.

She doesn’t know why Pinkie (Sam Riley, doing a bad Leonardo DiCaprio impression) approaches her and pretends to like her. She lets him pretend.

You want to smack her while she’s on her “date” with Pinkie — and therein lies an insight to her essential weakness. She’s the kind of girl one wants to smack. She’s exasperatingly, willfully blind, even more so after Pinkie points to the St. Christopher medal around her neck and tells her he understands her because they’re both “Romans.”

In establishing their shared Catholicism, they also seem to agree that they represent the different ends of the spectrum: Rose is going to heaven, and Pinkie is most certainly not. Somehow that only makes her love him more. No wonder her boss at the tea shop, the blousy Ida (Helen Mirren), wants to set everything straight again — she sees Rose as a hapless early version of herself.

One feels oddly out of time in Brighton Rock — which is particularly odd because the film is actually quite chronologically specific. At first, watching these hoodlums chase one another through those gloomy streets, one guesses it’s a postwar film (like the original 1947 film, based on the 1938 Graham Greene novel). Neither do the clothes or the sets betray anything different. But when suddenly a lush Doris Day standard fills the corners of the rooms and the characters start talking about out-of-control youth, you feel disoriented (what year is this, anyway?); and when gangs of Mods and Rockers descend on Brighton you realize it’s set in 1964.

One could say a lot of things about that weird chronological uncertainty — that it reveals a lack of focus by the director, or a deliberate attempt to keep us disoriented. Setting aside its effect on the film overall, it has a fascinating impact on our view of Rose.

For Rose is also out of time — lost, left behind. She pilfers a tenner from Pinkie’s stash of bills to buy herself a great new outfit, yet she enjoys the exhilaration of la mode fashion for only a moment before the self-consciousness and guilt overwhelm her. Not to mention the fact that the pink dress and white tights only exaggerates her youth, undermining any glamour. Rose could never be a part of the zeitgeist, never stutter along to The Who’s “My Generation.”

Watching Andrea Riseborough inhabit this role, one would never guess she was 29 at the time of filming — 29, playing a 15-yr-old so completely. Rose doesn’t appear to be the protagonist of this film till quite far along, but she sneakily steals the story from the ridiculous Pinkie and Ida and all the other characters who seem to possess so much more self-assurance and self-direction.

And in the end, perhaps it’s her failures to grasp the big picture — her failure to understand or join her own time — that grant her grace, for they mirror her belief that God loves her despite all her foolish actions, despite her sins.

Brighton Rock can be strangely overwrought and kinetic, not quite a noir and not quite anything else, either; I quite enjoyed it but wouldn’t go far to trumpet its achievements. If you see it, watch it for Riseborough’s sake. This young actor has gone on to receive many nominations and prizes for her work, but this part is a small revelation. I’m keeping my eye on her.