In two recent episodes of "Lost," John Locke told a few lies, killed an "Other," blew up a hatch full of communication devices and then set off more explosives in the Others' submarine to prevent anyone from leaving or arriving on the island. Now he's in the presence of his nefarious father, who's popped up on the island.

It's a far cry from the weeks he spent in a hole in the ground last season, punching computer buttons, only to emerge feeling like he wasted his time.

"Lost" mythology has cast Locke, played by Emmy-nominated Terry O'Quinn, as the show's most enigmatic character. When Locke has his mojo, it seems, so does "Lost."

In fact, the arc of Locke, and even O'Quinn's own story, closely parallel the highs and lows of the ABC ensemble drama that changed television three years ago. Now, 80 days into the journey of the plane-crash survivors, what most viewers intuited from the beginning seems to hold true: Locke is one important dude.

But is he the most significant castaway? The creators of "Lost" would never say anything that definitively, but they were willing to offer a glimpse of the way they've embedded some of the series' most telling elements in his story from the beginning.

Co-creator Damon Lindelof confirms that in the end, Locke will be among the ones who matter most. Executive producer Carlton Cuse added this: "The character of John Locke is just the very heart of the show."

When Locke boarded Oceanic Flight 815, he was in a wheelchair. But when the plane crashed, he could walk, and that seemed to bond him to the island forever. The episode two weeks ago finally revealed how he became paralyzed: His con-artist father, who years ago manipulated Locke into giving him a kidney, pushed him out a high-rise window, hoping to kill him. Then it did what "Lost" does. It delivered a whopper: Locke's father is tied up and gagged on "Other" territory.

"That was a big 'What?!' " O'Quinn said, describing how he felt when he read the script.

RIDE OF FRUSTRATION

Mysteries, loads of them, are the hallmark of this series, sometimes frustratingly so. Since "Lost" returned in a new time slot in February after a three-month hiatus, it has shed nearly 2 million viewers, although it still ranks as a top-10 show among the advertiser-coveted 18- to 49-year-olds.

As a fan of his own show, O'Quinn says he understands the audience's frustrations with schedule changes and the questions that outnumber the answers on the series.

"If I take Locke's story individually and just follow it from its beginning point to now, to me it's cohesive and it's understandable and it's interesting," O'Quinn said. "But because there are so many people, it's very patchy. It comes in fits and starts, and that's tough for the fans of the show to have to work to tie everything together."

In the first season, Locke was a self-assured survivor who motivated Jack (Matthew Fox) to leadership, helped Charlie (Dominic Monaghan) work through his heroin addiction, built a crib for Claire's (Emilie de Ravin) baby and insisted that they blow open the hatchway. Locke also sacrificed fellow castaway Boone's life, deliberately broke a transceiver, won his round against the menacing polar bear and dared to look inside "the eye of the island."

"I would get mail and e-mails from people that said the character had given them hope," O'Quinn said. "It was touching, and I thought the character was serene and strong. But then he became weak and addled, and I was upset that a strong card had become a weak card."

After the castaways went down the hatch in the second season, Locke was more than happy to save the world by pushing a button every 108 minutes. But when he learned that the hatch is supposedly a psychological experiment, he assumed the task he had been performing was meaningless, and that's when his faith began to unravel. Slowly, Locke regressed into the man he had been before the crash: a depressed office worker with no direction. And O'Quinn's discontent mounted.

"It's interesting because the actor took a parallel journey to the character," Cuse said. "Terry's frustration was really a good thing. And his growing disillusionment with his role was also a really good thing, because that's exactly what we wanted the character to do."

LIKE ATLAS

As the creators dreamed up Locke, Lindelof couldn't help but think of the Charles Atlas comic-book ads he saw as a child: the scrawny kid who gets sand kicked in his face by a bully, then lifts weights and whacks the bully in the face when he returns.

"I think that's basically who John Locke is," Lindelof said. "We keep showing you stories about him making bad decisions and being abused and conned and suckered, all because he wants to be loved. Now, he's on the island, he's not preoccupied with needing to be loved anymore. He just wants to know his place in the world, which I think is something Terry is also experiencing."

Fans have surmised that Locke was named after 17th-century philosopher John Locke, who theorized that the mind is a tabula rasa — that is, individuals are born with a clean slate, without innate mental content, and build knowledge from their experiences.

"Lost's" Locke lived a life marked by pain and disappointment until he regained his ability to walk on the island, which he interprets as a sign that destiny brought him there to give him a second chance. In this way, Cuse said, the character is a springboard to explore the issue of faith versus empiricism.

"The very original idea for Locke was that we needed a character who was going to have some sort of mystical quotient going on with him," Lindelof said. "He was going to be very mysterious and quiet. This plane crash is the best thing that's ever happened to this guy."

Whether Locke holds the key to the deepest mysteries of the island, O'Quinn has no idea.

"I don't know how central he is," he said, "but ... it usually means something when he's around."

O'Quinn fit the role, Cuse said, because, like Locke, he "marches to the tune of his own drummer." The actor often walks two hours barefoot on the beach from his North Shore home to the set.

"While all of the other actors are gathered in Kailua or Lanikai, the populated side of the island, Terry has set up camp away from civilization," Cuse said. "In many ways, he has the qualities of a kind of powerful and intuitive loner ... in close parallel to Locke as a character. He's a self-reliant guy who really forged a life outside his work as an actor, and I think that gives him a quiet strength."