A distant explosion rings through the jungle.

Jack Bauer, longtime protagonist of the Fox show “24,” stiffens, a spasm of muted pain on his face. One of his closest friends has just sacrificed himself to a land mine, taking bad guys with him. Jack has no one to tell; as so often in “24,” we the audience are the only ones who see his suffering.

Jack Bauer is a tragic protagonist, in the classical/Shakespearean mold. And the show’s creators know it.

“He’s kind of like Job,” says Howard Gordon, executive producer and showrunner of “24.” “It’s a case of your character being your fate, as Heraclitus says.”

A television producer invoking the Old Testament and a pre-Socratic Greek philosopher? “Well, the show IS a tragedy,” Gordon says, in a phone interview. “We weren’t even aware of it when we started with the character of Jack. But this whatever-it-takes mentality — it comes with a toll.”

For six seasons (the seventh started last night and continues tonight on Fox with a second two-hour show), Jack, played by Kiefer Sutherland, has battled terror with single-minded bravery, tolerance for pain and disregard for conventional morality. (He is renowned for ends-justify-the-means ethics, torturing suspects or going rogue if he sees no other way to defeat the terrorists.) On the way, he has lost every important human contact. His wife died in season one. He is estranged from his daughter; love interests flare up and burn out. Most close colleagues either have died or are his enemies now. Jack is an isolated hero in a thankless world. (Well, he’ll always have Chloe.)

“There was some pushback, both from Fox and from Kiefer, about making him quite so tragic,” says Gordon. “But as the first season went along, we saw this was how it had to be for Jack.”

Tragedy occurs when a person is destroyed by the very attributes that make him or her admirable. You don’t need to die to be tragic; sometimes it’s enough to suffer. Oedipus is destroyed by his insistence on knowing the truth; Othello by his noble standards and naive trust; Macbeth by his high-minded ambition. As Eric Mallin, associate professor of English at the University of Texas, reminds us, tragedy happens “when one’s virtues and goodnesses bring about a fall, and when suffering is … not fully understood.”

That fits the bill with Bauer. This is no show in which virtue is rewarded. Jack has been tortured as much as he has tortured, climaxing when he is kidnapped into slavery in a Chinese prison for almost two years. Neither Jack nor the audience fully understands why he has to suffer so much. That’s the clammy touch of fate.

Jack is part of a class of tragic figures on TV. Classmates include Mafia kingpin Tony Soprano (James Gandolfini) of HBO’s “The Sopranos,” which ran 1999-2007; New York legal sharkette Patty Hewes (Glenn Close) of the FX show “Damages”; Dr. Gregory House (Hugh Laurie) of the Fox show “House”; and Dexter Morgan (Michael C. Hall) of Showtime’s “Dexter.”

TV’s penchant for morally ambiguous characters was spurred by the watershed 1980s NBC shows “Hill Street Blues” and “St. Elsewhere.” These shows told stories in novel, complex ways, abandoning one-shot episodes for long-running, multi- layered plots. These featured complex, long-suffering characters such as Lt. Norman Buntz (Dennis Franz) of “Hill Street” and Dr. Donald Westphall (Ed Flanders) of “St. Elsewhere.”

That’s solidly in an American vein: the maverick do-gooder, the sheriff, doctor, lawyer, detective, cop who risks life, love, family and future to do the right thing. It’s the underside of our romance with the American hero, a myth about the cost. Ironically, especially in “24,” a show so closely associated with 9/11, there’s a hint that the right thing may not always be worth it.

Today there are so many TV antiheroes that Newsweek’s Joshua Alston recently lamented the “antihero overload,” writing that “no one on TV can be merely good or evil anymore.”

Jack Bauer is certainly neither. There is much to admire in him, much that is, as Gordon says, “noble,” including his loyalty, his love of freedom and democracy, and his awareness of the needs of others: “In a way, he’s a highly moral character.”

There is also much not to admire. As Rich Moran wrote for the conservative webzine American Thinker: “Bauer doesn’t stretch the Constitution. He shatters it into a million pieces.” He tortures his own brother to get terror-related info, and shoots his mentor’s wife in the leg when she won’t tell him where he is.

There’s much needless death, pain and suffering. (Newsday columnist Raymond Keating estimates Jack has directly or indirectly killed 167 people in the first six seasons.) He also has captured or thwarted a lot of criminals, but the question remains: at what price?