On tonight's major new episode of Fringe, Olivia travels back to her alternate reality and meets, once again, with William Bell.

The mysterious character is played perfectly by Leonard Nimoy, who described Bell as "brilliant, wealthy and very powerful" in an interview with Reuters this week.

But is he good or evil?

"Time will tell," the actor said, adding: "The character was somewhat a blank slate and therefore attractive because there is an opportunity to build an interesting and unpredictable character."

Overall, Nimoy is simply thrilled that Fringe wanted him at all.

"I am very flattered that people are still finding me useful," he said. "I still feel strong and healthy and active, and as long as there is interesting work to do, I'll probably keep on doing it."

We'll post a detailed recap of "Momentum Deferred" soon after it airs tonight. For now, check out this preview of events and photos from the episode.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.