Hopeful, breathless, even fretful over what may lie ahead or be forever unexplained, "Lost" fans have welcomed back the ABC mystical thriller for its sixth season _ the beginning of its long-coming, too-close-for-comfort finale.

Two of the final 18 hours were aired Tuesday as its season premiere, after a warm-up "Lost" for Dummies recap that, even for the most devoted disciple, offered helpful cues to the ever-escalating mythology.

But did this double-dip opener address the pair of island mysteries gnawing at viewers since last May?

What was the upshot of the kookie nuclear explosion Jack (Matthew Fox) masterminded to rewrite history and render the series' whole storyline moot? And what's the scoop with the dead John Locke (Terry O'Quinn) coexisting with his very-much-alive John Locke look-alike?

(Warning: possible pesky spoilers ahead.)

Well, Jack is seen back on Oceanic Airlines Flight 815, and despite several moments of troubling turbulence, soon enough all seems well.

"Looks like we made it," Jack says to a fellow passenger as the flight smooths out.

Was this a replay of the original flight, just before the plane was pulled apart by electromagnetic energy and crashed in the series premiere?

Maybe Jack's grand plan to prevent the crash didn't work.

Or maybe it did.

Then the action shifts to the island and the construction site of the Swan station, where the nuclear bomb had been detonated to cap the deep pocket of electromagnetic forces. Jack, Kate (Evangeline Lily) and Sawyer (Josh Holloway) are bloodied and shaken up by the explosion.

And Juliet (Elizabeth Mitchell), who set off the nuke after plunging to the bottom of the shaft, is found by Sawyer alive. Alive long enough for their tearful farewell, anyway.

Elsewhere, the island's uber-boss, Jacob (Mark Pellegrino), who was apparently stabbed and burned to death in last season's finale, seems in fine fettle long enough to declare, "I died an hour ago."

As for the live version of Locke: Seems as though this is the human alter ego for the mysterious Smoke Monster, which has plagued the islanders in the past.

"I'm sorry you had to see me like that," he tells Ben (Michael Emerson), who is shocked by the sight of the carnage inflicted on Jacob's thuggish security guards.

"What are you?" asks Ben when the monster reverts to Locke's human form.

"I'm not a what, Ben. I'm a who," says ersatz Locke.

"You're the monster," says Ben.

"Let's not resort to name-calling," the Locke character says.

Then this creature that looks like Locke delivers a tribute to the real and real-dead Locke: "He was weak and pathetic and irreparably broken. But despite all that, there was something admirable about him: He was the only one of them who didn't want to leave. The only one who realized how pitiful the life he left behind actually was."

Halfway through the program, the passengers of Oceanic 815 _ including Locke, Jack and other favorite characters _ are seen deplaning after the jet has safely landed in Los Angeles. Oddly, they mostly appear less than happy to be there, unhappy with themselves and with their lives. Even pitiful in their lives.

During this, which is perhaps some sort of alternate narrative device on which "Lost" thrives, Jack and Locke are thrown together at the airport for a brief conversation. Jack, a spinal surgeon, asks why Locke is in a wheelchair.

"Surgery isn't going to do anything to help me," says Locke, little suspecting that, once on the island, his paralysis would miraculously be cured. "My condition is irreversible."

"Nothing is irreversible," says Jack with a doctor's confidence.

Jack could have been talking about the stirring, often murky, sometimes overreaching "Lost" premiere, on which even Sayid (Naveen Andrews) comes to life after apparently dying from a gunshot wound.

Nothing is irreversible. Except, apparently, the end of "Lost" just weeks from now.

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EDITOR'S NOTE _ Frazier Moore is a national television columnist for The Associated Press. He can be reached at fmoore(at)ap.org