Uneven is probably the best word I can use to describe Bryan Singer’s “Apt Pupil,” the story of a boy who seeks a tour through humanity’s dark side.

Todd (Brad Renfro) is a gifted high school student; he’s so gifted that when his history class spends a week learning about the Holocaust, he hits a university library to learn more about it. And he’s so smart that when he sees a suspicious man on a nighttime bus, he begins an amateur investigation that will lead to shocking truths about humanity and himself.

See, that man turns out to be Kurt Dussander (Ian McKellen), a high-ranking Nazi who has been on the run from his past for 40 years. After the investigation, Todd confronts him and proposes a deal: in exchange for his silence, Dussander will tell Todd his story with no horrors spared.

Of course, Dussander agrees and of course, Todd gets a bit more than he sought: for better or for worse, he owns that man and he gets to experience first-hand the intoxicating rush of complete control of another’s fate.

But well, things can’t stay that rosy for too long; Dussander helps Todd out in a pinch, and in return discovers that as much as Todd can hurt him, Todd has waited too long to tell the truth now. The “sudden but inevitable betrayal” (from “Firefly”) turns Todd into the owned one as he fights for the sanctity of his future.

Here’s where the unevenness of the movie comes into focus; at about the hour mark, an event occurs that truly strains credibility from both the main characters. Not too long after that, another event of dues-ex-machine proportions occurs that makes the final ending just a little too easy. Without giving the twists away, I’ll just say that the final events don’t seem real (with the exception of the very last scene, where the pupil demonstrates the he has mastered Dussander’s final lesson).

But most of that is not the point of the film, which is to showoff McKellen’s stellar acting as an unreformed man who longs for the good old days of the horror machine. Dussander recounts his tales without remorse or regret, and he becomes that most elusive of movie villains, one that is both pure evil and totally human. It’s quite a trick and it’s worth sitting through the crap second half to watch.

There are better movies to see McKellen in, most notably his Oscar-nominated performance as director James Whale in “Gods and Monsters,” but if you need a McKellen fix, “Apt Pupil” will do.

“Apt Pupil” (1998)

Directed by Bryan Singer

Written by Brandon Boyce

Starring: Ian McKellen (Dussander)

Brad Renfro (Todd)