Provided you don’t think too hard about its many gaps in logic, the new Liam Neeson vehicle “Unknown” proves to be a modest winter surprise: A Hitchcockian thriller with a slick modern gloss.

All the classic tropes are here: the case of mistaken identity; the innocent man at the center of what appears to be a baffling international conspiracy; the beautiful blonde who can’t possibly be trusted. But Neeson and director Jaume Collet-Serra filter them through a modern Hollywood action-movie prism.

Sure, Hitchcock was far more concerned with psychological gamesmanship and slow-burning suspense. But at least “Unknown” knows how to throw a good punch.

Neeson plays Dr. Martin Harris, who is traveling to Berlin with his beautiful wife (January Jones) to deliver the keynote speech at a biotech conference. After a mix-up at the taxi stand, he accidentally leaves his briefcase at the airport, setting off a chain of events that ultimately sends him into a four-day coma. When he wakes and tracks down his wife at their hotel, she insists that she doesn’t know this ranting lunatic. In fact, Dr. Martin Harris is standing right next to her, and now he’s played by Aidan Quinn.

Do you really buy that Neeson’s fastidious, detail-oriented character would be so careless as to misplace a briefcase — one stuffed, inevitably, with important documents? Would he really end up crossing paths with an immigrant cabdriver (Diane Kruger) and a brilliant ex-Stasi officer (the excellent Bruno Ganz), both of whom willingly help this delusional-sounding stranger? Probably not.

But “Unknown” has a couple of aces up its sleeve. For one thing, the hulking Neeson commits fully to the anguish of a man who fears he may have lost everything. As in last year’s “Taken,” he gives the sometimes dopey material far more weight than it deserves. (The film is based on a novel called “Out of My Head,” by Didier Van Cauwelaert; the screenplay adaptation is by Oliver Butcher and Stephen Cornwell.)

More critical is the fine work of director Collet-Serra, who after getting his start in commercials and music videos and directing a couple of ho-hum horror pictures (“House of Wax,” “Orphan”), has neatly hit his stride. “Unknown” has plenty of frantic chases, gunfights and explosions, but the director manages to stage at least two sequences — one in which Neeson’s character is drugged and nearly killed in a hospital, another in which he eludes an assassin inside an art gallery — with patience and old-school bravura.

He also does a splendid job of capturing Berlin, the famous sights and the dingy, out-of-the-way alleys. As Alfred Hitchcock probably would have been the first to tell you, a little bit of travelogue goes a long way in distracting an audience from plot holes.

Film focus

WHAT: “Unknown”

RATED: PG-13 for violence, mild sexual content

RATING: 3 out of 5 stars

RUNNING TIME: 113 minutes

Liam Neeson and January Jones appear in a scene from “Unknown.”

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