He may forever be known as Spock to Trekkies, but Leonard Nimoy is carving out a new set of fans for himself, courtesy of his key role on Fringe. The veteran actor appeared on the show's May finale as William Bell, Walter's arch nemesis.

Now, viewers can circle October 8 on their calendar.

That's the date on which Nimoy will reprise this character. The episode will feature a flashback by Olivia to her previous alternate-reality encounter with Bell.

According to producer Jeff Pinkner, Olivia will obtain a “further understanding of what Bell and Walter Bishop hoped to accomplish when they experimented on her as a child."

During the same installment, look for another new woman (portrayed by Theresa Russell) to show up. As reported by TV Guide Magazine, this female was also experimented on by Bishop.

As for other season two storylines, look for multiple Observers to be featured on a future episode.

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