As Liam Neeson has demonstrated - to the tune of $226 million, the worldwide take for Taken - the tall, sad-eyed actor can play action hero, handily. With his soulful gaze and crooked nose, his seeming reluctance to throw a karate chop but his deft ability to do so, Neeson has an air of melancholy and menace - you feel sorry for the guy, and wary of him at the same time.

And now, in the similarly succinctly titled Unknown, a tricky yarn set in a gray, wintry Berlin, Neeson is back, scrapping with bad guys, careening up one-way streets and onto sidewalks, doing damage with shards of glass and metal objects, all with a knack and focus usually not associated with the skill sets of a New England college professor - which is what he's playing in Jaume Collet-Serra's propulsive thriller.

Dr. Martin Harris, a biotech researcher, has landed in Germany in the company of his beautiful wife, Elizabeth (January Jones), for an important conference in which he is planning to make an important presentation. But as the couple check in to their luxury hotel, he realizes he has left a bag at the airport, and so, without a word to the missus, he turns around, climbs in a cab, and impels the driver to step on it back to Schoenefeld Airport.

This the driver does, with rather calamitous results. If you've seen the trailer, you know that the cab goes off a bridge, and that when Neeson's character wakes from a coma after four days in a hospital bed, his very identity seems to be in doubt: Someone has taken his place at the conference, and taken his name, and taken his wife, too. And she seems to be fine with it.

"I'm not crazy!" he insists. "Somewhere there's proof that I'm me!"

And so, for the next hour and a half, Dr. Harris goes tearing around in search of said proof, accompanied, a good deal of the time, by the one Berliner who knows his story to be true: Gina (Diane Kruger), the multi-pierced, undocumented Bosnian who started this mess in the first place when her taxi went sailing into the Spree. So, who is this new Martin (Aidan Quinn), and why does Elizabeth seem fine sticking by his side, and seem a little freaked out at Neeson's insistence that he's her husband?

It's all very Hitchcockian, at least for a while. And clever and exciting, too, even if the convergences begin to strain credulity, and, when you think about it, defy logic, too.

Collet-Serra, the Spaniard who directed Vera Farmiga and Peter Sarsgaard in the adoption nightmare Orphan, proves adept at the quick cut and a decent choreographer of fights and chases, too. There are times, in both its tenor and its plotlines, when Unknown may be remindful of The Bourne Identity - another case of fuzzy memory, with a European actress as the cash-strapped hipster who becomes an accidental partner in the hero's search for himself. (Run Lola Run's Franka Potente had the honors. What's become of her?)

Midway through Unknown, the wonderful Bruno Ganz shows up in the guise of a former Stasi agent - the East German secret police, a confrere to the sad-sack spy of The Lives of Others - who now freelances, sleuthing and deducing with a seasoned certitude. Droll but a bit bilious, Ganz's Ernst Jürgen is recruited to help the real Dr. Harris - if, indeed, Neeson's guy isn't suffering from trauma-induced delusions - find out what's really going on. Even later in the game, Frank Langella makes an appearance as the departmental head at Harris' college. Rarely has academe seemed so sinister.

Ultimately - and doesn't it almost always come to this? - Unknown lets things down as it wraps things up. It's the very rare thriller (Michael Clayton is the one that comes to mind) where the resolution proves as satisfying, and smart, as the premise. Unknown is not that, but with Neeson at its center, it's well more than passable.EndText

Contact movie critic Steven Rea at 215-854-5629 or srea@phillynews.com. Read his blog, "On Movies Online," at http://www.philly.com/philly/blogs/onmovies/