In Berlin on business, an American man arrives at his hotel only to discover that he’s left an important briefcase at the airport. Without even telling his wife, he summons a taxi and hurries away. Won’t he be sorry. The taxi plunges off a bridge and the man wakes up in a hospital four days later. Without his precious briefcase. And for that matter, without his wife, who no longer recognizes him and apparently has consented to another man taking over his identity.

These things usually have a perfectly implausible explanation, most often to do with some sort of deadly espionage. Anyway, being Liam Neeson, the man doesn’t take it lying down. Well, OK, there is one part where he has to lie down because he’s been sedated and strapped into to a gurney by a medical professional with an alarmingly faulty understanding of the Hippocratic Oath. But after that our man definitely is up and about, quite determined to get to the bottom of his dilemma.

And it is sort of touching to find Liam Neeson grappling with a crisis of identity. Remember in “Schindler’s List” when he regretted not having done more to help? Remember in “Taken” when he killed more people (without regret) than most Nazis ever did? Remember in “Clash of the Titans” when he had a big beard and phosphorescent armor and was supposed to be Zeus? Good, because there is not much in “Unknown” worth remembering.

Let it just be said that given a wife played by January Jones, with her usual vacancy, and a taxi driver played by Diane Kruger, with a tad more élan (and only a tad is required), he might have considered taking better advantage of his situation. True, it was the driver who sent him off that bridge, but it was also she who retrieved him from the frigid river below, only later to say, “What matters is what you do now.” But of course there is the pressing issue of restoring his selfhood, redeeming his honor. Possibly. The movie isn’t sure. It’s distracted. It has a rickety twist to protect. Other involved persons include Aidan Quinn as the apparent impostor, Bruno Ganz as a seasoned ex-Stasi investigator, and Frank Langella as a mysterious acquaintance from back in the U.S.

Judging by the steely gray Middle-European atmosphere, the ominous wrong-identity plot, and the peppering of skeletally pretty blonde nonentities, “Unknown” aspires to be an old-fashioned thriller like they used to make back when there was an East Germany. Its denouement, however, would seem to result from a quick study of 1980s action movies. (A slower study of 1980s Roman Polanski movies might have been more useful.) It also has a few colorful, choppy flashbacks, put in for effect and for explanation. The writers are Oliver Butcher and Stephen Cornwell, adapting Didier Van Cauwelaert’s novel “Out of My Head,” and the director is Jaume Collet-Sera, whose previous forgettable wintry thriller with an identity twist was 2009’s “Orphan.” Finally, editor Tim Alverson seems to have cut every scene as if trying first to conceal and then to apologize for what it contains.

This much about “Unknown” should be known: The American man’s reason for being in Berlin was a biotechnology conference; the espionage is agricultural. More than once, someone explains that what’s really at stake here is “a new strain of corn.” Indeed.