Jesse Eisenberg has made more movies than you realize, and in most of them, he can be seen worrying at one time or another. In “Roger Dodger,” which introduced him to most of us in 2002, he fretted about his ability to attract women. In “The Squid and Whale” he was concerned over the choppy relationship between his parents. In “The Social Network” - playing Mark Zuckerberg - he wasn’t sure if his big gamble on the startup eventually called Facebook would work. In “Zombieland” he was freaked out because he had to fight zombies.

In the darkly comedic drama “The Art of Self-Defense,” Eisenberg has the lead role of Casey, a bright, meek, and introverted accountant who’s probably used to living alone - with only the company of his cute little dachshund - to being shunned by co-workers, and to being bullied. But a full-out mugging, replete with kicks, punches, and some bloodying up gets him to thinking about making changes in his life.

He decides to buy a gun. But, no, that’s not his style. So he looks into, likes what he sees, and signs up for karate lessons at a small-time, no-frills dojo that’s run by a low-key but charismatic, yet decidedly mysterious fellow who calls himself Sensei, the Martial Arts word for teacher.

And soon Casey, with time off from work to recover from that beating, is among the handful of men - and one woman - who attend Sensei’s classes, where rules posted on a wall are as important as instruction. Rules such as “No shoes on the mat” and “Stay hydrated” and “Guns are for the weak” and “Tap or take a nap.”

It’s a strange new world for Casey who, though not exactly fitting in right away, notices that Sensei regularly approves of his commitment and progress. But the same can’t be said for the other guys in the class, some of whom eye him warily, or of Anna (Imogen Poots) who besides taking classes, also teaches karate to kids at the dojo, and has an inexplicable chip on her shoulder.

The film gets into the history of and stories behind the colors of karate belts, and peeks in on both the camaraderie and the competitive spirit among the members of Sensei’s class. Sensei speaks in a deliberate manner, obviously believing every word he says, and trusting his students do, too. He takes no guff and won’t put up with slackers. He might have a sense of humor hiding behind a slight twinkle in his eye. Or he might be a psychopath.

It hints that he has a different-than-expected interest in Casey’s evolution in his classes. “Why are you REALLY here?” he asks the ever-improving student, before explaining his own method of teaching: “You’re a blade and I’m sharpening you.”

But that’s an easy-to-understand remark, especially when it’s held up against another Sensei-ism: “You must kick with your fists and punch with your feet.”

While that’s sinking in, the film dives headlong into new territory - the existence and exploration of Sensei’s secretive night classes. This signals a move from the light into the dark, and it brings forth more of Sensei’s rules: Listen to metal music, learn to speak German, drink your coffee black, never hold back.

Casey goes through some major changes, Anna goes through some major changes. Sensei … let’s just say he’s not the man we thought he was, and that he has more than a couple of sides to him, and one of them is brutal. Yet, in a great performance by Allesandro Nivola, he remains mostly low key, and ever more mysterious.

Everything builds to an odd, revelatory climax. And the script features a terrific line, one that comically negates so much that came before it: “I didn’t play by the rules, but there never were any rules.”

Ed Symkus writes about movies for More Content Now. He can be reached at esymkus@rcn.com.

“The Art of Self-Defense”
Written and directed by Riley Stearns
With Jesse Eisenberg, Allesandro Nivola, Imogen Poots
Rated R