There’s a sameness to many of the roles Liam Neeson takes these days. With a few notable recent exceptions that still prove his depth and range. The quality of these films fluctuates between satisfying and disappointing, for the same reason. Because Neeson is so adept at rendering this stock character, he doesn’t always work very hard at it. Sometimes that effortlessness is a pleasure, and sometimes it just feels lazy.

In plot, at least, Memory is no exception. Based on the 1985 novel De Zaak Alzheimer by Belgian writer Jef Geeraerts and its 2003 Belgian film adaptation, The Memory of a Killer, Neeson’s latest genre exercise centres on a hit man with dementia who suddenly sprouts a conscience when one of the targets he’s been hired to kill turns out to be a 13-year-old girl. And yet Memory is a cut above average, for this sort of thing. Mostly that’s thanks to the direction of Martin Campbell, who injects the same freshness of energy into this formulaic outing that he did with last year’s assassin thriller The Protege.

Memory feels more like film noir – deliciously dark, cynical and slightly amoral – than a pulpy piece of rote storytelling.

Neeson, for one thing, isn’t really the good guy here, or really even the bad guy with a heart of gold. His Alex Lewis is a coldblooded killer. With one exception – the barely teenage courtesan (Mia Sanchez) Alex refuses to kill after he’s hired to kill a couple of people to cover up a child-exploitation ring – he has few qualms about whom he murders. Cops, in particular, are so much collateral damage in Alex’s single-minded mission to take out the members of the international sex-trafficking cartel. The fact that he’s starting to lose his memory, and must write reminders down on his forearm with a Sharpie, barely makes him more sympathetic.

It’s a weird feeling, not being able to root wholeheartedly for Neeson. But we kind of like it. It feels honest, and less pandering.

Memory is by no means a deep film. But there’s something here that lends the familiar proceedings a bittersweet aftertaste that lingers in the mind. That’s the film’s mix of moral ambiguity and the regret of someone for whom it’s too late to undo the past, but not perhaps to rectify the present, even when the law can’t.