One of the finest movies of the year is a thriller about the tracking and, finally, slaying of Osama bin Laden.

“Zero Dark Thirty,” which is a slang reference for the wee hours of the morning, is embellished with fictional touches, but it is based on fact. It’s not an easy movie to watch, but its compelling realism is riveting. And with director Kathryn Bigelow at the helm, it creates the same sort of tension and atmosphere as her Oscar-winning “The Hurt Locker.” And, like “The Hurt Locker,” it’s a fascinating character study as well.

The movie begins in complete darkness with only audio from 9/11. That sets the stage for the next scene in which CIA agent Maya (Jessica Chastain, “The Help”) watches as a suspected terrorist is interrogated by Dan (Jason Clarke). The terrorist, who may have been part of al-Qaida, is physically tormented while Maya watches.

Dan returns to the United States and Maya takes over the investigation. She remains determined to continue and believes that she can find bin Laden, the terrorist leader behind the 9/11 plot.

We already know how the movie is going to end, but that doesn’t mean that getting to the finale is not suspenseful. Bombings and other surprises will have your pulse racing as you watch historical events unfold. Some of the facts have been enhanced by sources who spoke confidentially to the filmmakers.

Of course, in the latter part of the film, we’re right beside the take-down team in an action-packed, hair-raising sequence that’s one of the best parts of the film.

As always, Chastain is outstanding. Within the past four years, she has taken Hollywood by storm, appearing in such mainstream hits as “The Help” as well as more obscure, but respected, films such as “The Tree of Life.” Her character is completely focused — obsessed, really — with the elimination of bin Laden, and she will stop at nothing to ensure that he meets his end. Chastain breathes life into her characters, particularly to that of Maya as a woman with only one purpose in life.

The movie deserves its lengthy running time. You won’t believe that its duration is more than two hours, particularly when lesser shows seem painful at a relatively brief 90 minutes.

If you’ve never seen Chastain, now’s the time to become familiar with this incredible actress before her name becomes a household word.