Devoted fans know "Lost" is full of surprises. Passengers of Oceanic Flight 815 die without warning. Those oh-so-creepy Others are always lurking somewhere. The cryptic clues of the Dharma Initiative are interwoven throughout the episodes. And seemingly good characters do very bad things.

But nothing prepared viewers for the jaw-dropping conclusion to the May 3 episode. In the nail-biting final seconds, a recently returned and visibly shaken Michael (Harold Perrineau) callously shot and killed Ana Lucia (Michelle Rodriguez) and Libby (Cynthia Watros).

"Even though it's not real, it still feels like you did something terrible to two people that you really care about," Perrineau said. "I have an eerie feeling every time I go into the hatch now. I don't like going in there."

Perrineau, the only actor series creator J.J. Abrams wanted for the role of Michael, was still adjusting to life on a top-rated series. "I had sort of like niche-audience kind of fame" before "Lost," he said. "This really opened me up to a lot more people." But Perrineau had been missing from the series for nine episodes after his character marched into the jungle to search for his kidnapped son.

An imposed hiatus is a scary prospect for any actor, but particularly on "Lost," a series not known for its job security.

"I was a little nervous about it," Perrineau said. "But we have really great writers, so I just sort of trusted in that and thought that my return would be really something interesting. And now that I'm back, it has been."

Interesting, yes. But how did Perrineau adjust to his character's astonishing transformation?

"The thing I have come to realize about Michael is that he's just a guy. He's not a killer or a con man or ex-drug addict," Perrineau said. "He's just a guy struggling to be. ... How far those struggles will push him — and who he becomes because of those things — are really interesting."

Executive producers Damon Lindelof and Carlton Cuse, who co-wrote this week's season finale, knew this was the journey Michael would have to take.

"As soon as Michael had the opportunity, we knew he would go searching for his son, and there wasn't anybody that would be able to stop him from doing that," Lindelof said.

Yet it was a risky decision to have the heretofore likable Michael go in such a dark and duplicitous direction.

"The character has evolved tremendously," Cuse said. "We've seen him evolve into being a guy who will literally do anything for his son and is willing to make tremendous personal sacrifices in order to get (him) back. His son moves from something that is a burden to being the absolute central most important thing in his life. Along with that kind of comes a sense of responsibility that this character didn't have at the beginning.

"Ultimately he's put into a horrible 'Sophie's Choice' kind of dilemma in terms of what he has to do in order to get Walt back," Cuse said.

Both executive producers said they think audiences will sympathize with Michael's cause by the finale.

"It's our expectation that the audience may not forgive him for murdering Ana Lucia and Libby, but that they will say, 'I would have done the same thing in his shoes,' " Lindelof said.

Meanwhile, Perrineau has cultivated his own hypothesis about exactly what the deal is with the mysterious island.

"I have a really slight theory," he said. "Lately, I'm thinking the Dharma Initiative reminds me of those guys who got together and all decided to start (their own) religions. Somehow, they've been creating some kind of experiment to create some sort of religion based on what humans do. ... It really is just this test of the human spirit, and how we make new rules."

And Perrineau warned that Wednesday's finale is going to be a doozy. "It's as shocking as last season, if not more."