"The Beast," which premieres tonight, feeds off two highly compelling story lines. One involves Charles Barker, a charismatic, crass FBI agent who's either a borderline superhero or a devious rogue who spends his off time stroking a cat and planning the destruction of the free world.

But that's nothing compared with the real-life drama starring the show's lead. Hours after learning that A&E had picked up the pilot a little more than a year ago, Patrick Swayze, who portrays Barker, revealed that he has Stage IV pancreatic cancer, which means the disease has spread to other parts of the body and leaves the afflicted little hope for a long future.

Although he faced tough odds and months of chemotherapy, Swayze and the network decided to go ahead and shoot an entire 13-episode season of a stunt-heavy, emotionally draining series in the unforgiving Chicago winter.

The results are miraculous, in terms of both the high quality of the final product and Swayze's take-no-prisoners performance. It's more dazzling and complex than any footwork in "Dirty Dancing."

It was in that long-ago blockbuster that Swayze established himself as a big-screen Romeo, going so far as to record a ballad ("She's Like the Wind") designed to make high-school girls swoon at senior prom. But he's never shown such a gritty, dark side -- and it can't be sheer coincidence that he's discovered it while facing his own mortality.

"Everyone who writes, directs and produces for the show is aware that he's bringing the force of his own personal struggle into this performance," said co-executive producer John Romano. "I think he feels that this show is kind of a statement at this point in his career."

Even without the ravages of cancer, Swayze, 56, hasn't aged particularly well. That's a good thing. The pretty-boy face that allowed him to pass as everything from a lovesick spirit in "Ghost" to a drag queen in "To Wong Foo Thanks for Everything, Julie Newmar" is now grizzled and lined, an advantage, of sorts, for someone eager to tackle more complex characters like Barker.

When producers met with him during the casting process, they were amazed at how much his face had changed over the years and how well it fit a character who doesn't hesitate to shoot a fellow agent during an undercover operation to avoid suspicion. It also helps suggest that he may be as villainous as his higher-ups suspect.

Barker's strength onscreen is only surpassed by Swayze's mettle on the set. Despite heavy treatment, the actor missed just one day of shooting. The only conflict he had with producers was when he complained that they were treating him too gingerly.

"He's such a man, you know," said Travis Fimmel, a relative newcomer who brings Ray Liotta-type intensity to his role as Barker's green partner. "The sickest thing about him on the set was probably his jokes."

But the events of last week were vivid reminders that Swayze has an incurable, life-threatening disease. First, he did an interview with Barbara Walters in which he admitted he was "going through hell." A few days later, he was scheduled to meet for interviews with various TV critics (including this one) in Los Angeles, but checked himself into the hospital with pneumonia hours before the appointment.

Swayze's illness won't affect the first season; taping concluded in November. Under normal circumstances, a second year would seem likely as "The Beast" fills the perennial need for morally ambiguous, run-and-jump cop drama, a role once played by FX's now-departed series "The Shield." Producers say they will take their cue from Swayze.

If he doesn't come back, Swayze fans can rejoice that he ended his career on such a high note, while those of us who underestimated him for so many years will be left wondering what might have been.

njustin@startribune.com • 612-673-7431