‘Imperium’: Daniel Radcliffe scary good as a skinhead infiltrator

If ever there were an inkling Daniel Radcliffe might fall victim to “Harry Potter and the Curse of the Post-Blockbuster Franchise Career,” said inkling never had a chance.

In the half-decade since the last “Potter” film, Radcliffe has shown an impressive versatility onstage and in the movies, from the Broadway revival of “How to Succeed In Business Without Really Trying” to his role as an animated corpse in the crazy-ass indie film “Swiss Army Man” earlier this year to perhaps his most accomplished onscreen role to date — that of an FBI agent who goes undercover as a white supremacist to infiltrate a potential domestic terrorist threat in “Imperium.”

We believe the diminutive but screen-commanding Radcliffe as an intense, idealistic, somewhat naïve federal agent — and we can see how even the most sophisticated among the ranks of the racist “soldiers” would buy into this guy as a disillusioned Black Ops veteran filled with hatred for blacks, Hispanics and Jews.

With his head shaved, spouting racial invectives dripping with so much hatred we cringe and sporting a flawless American accent, Radcliffe is so far removed from the Harry Potter character a casual observer might not even realize it’s the same actor.

“Imperium” (it means “authority to command”) is based on the real-life experiences of former FBI agent Michael German, and if even a third of this stuff happened to German, one imagines he’ll spend the rest of his life trying to shake it off.

Radcliffe plays Nate Foster, a smart but inexperienced young agent tabbed by his supervisor, the wisecracking, gum-cracking Angela Zamparo (Toni Collette), to go undercover and join a neo-Nazi organization that could be graduating from hate-filled websites, underground radio shows and parades to a dirty bomb attack in a major American city. (Sidebar: Collette is an accomplished and very likable actress, but whoever OK’d the choice for her to chomp theatrically on her gum throughout the movie to the point of distraction was doing her no favors.)

Nate memorizes his new back-story, including the details of his tours in Iraq and his reasons for wanting to join the “movement.” Even if his new buddies show up unannounced at his new apartment to check for any signs he’s a cop of some kind, they’ll find nothing.

Some of the skinheads are your clichéd Nazi-loving boneheads who are just looking for an excuse to spew their hatred among like-minded idiots, and an outlet for their urge to commit irrational violence against minorities.

Others are educated, sophisticated, outwardly rational believers in the cause — which of course makes them much more chilling and infinitely more dangerous.

Sam Trammell (“True Blood”) is a soft-spoken, well-read, classical music-loving family man who comes to think of Nate as a kindred spirit and invites him into his home, to listen to Brahms and share meals with his devoted wife and his two young children, who already are being brainwashed with white supremacist propaganda.

As is almost always the case with these undercover films, from “Donnie Brasco” to the recent “The Infiltrator,” our hero finds himself empathizing with the very figure he’s tasked with taking down — leading to the obligatory scene where the boss has to remind him of his mission. So yes, “Imperium” follows a familiar path, but does so with intelligence and plausibility at nearly every turn.

As written and directed by Daniel Ragussis, “Imperium” is filled with a half-dozen other supporting characters as compelling and (in some cases) just as unsettling as the neo-Nazi who wears comfortable sweaters and has built a tree house in his suburban backyard for his kids. The most memorable is Dallas Wolf, a right-wing fringe radio host who has authored a modern-day “Mein Kampf” titled “Genocide: The Murder of White America,” and is attracting increasingly larger crowds on the lecture circuit.

Does this charismatic lunatic actually believe the hate he’s selling — or is it shtick to attract listeners and sell books? As Wolf, the brilliant Tracy Letts keeps us guessing until at long last all the cards are on the table.

On a number of occasions, it appears as if Nate will be found out. Each time, the screenplay and the actors take us to a place we find credible — and not always predictable. “Imperium” is a well-spun, tight thriller, thanks in no small part to Radcliffe’s excellent, sharply focused performance.

★★★1⁄2

Lionsgate Premiere presents a film written and directed by Daniel Ragussis. Running time: 108 minutes. Rated R (for language throughout). Opens Friday on demand.