Fans of Michael Emerson‘s turns on Person of Interest, Lost and/or The Practice may get a hint — but only a hint — of his previous TV work when he arrives to make mayhem on The CW’s Arrow this fall. Fall TV Cast Changes: Leaving & New Actors

As trumpeted at the San Diego Comic-Con last month, Emerson is set to recur during Season 6 (premiering Thursday, Oct. 12 at 9/8c) in an undisclosed mystery role. During TVLine’s Fall Preview Q&A with co-showrunner Wendy Mericle, it was confirmed that Emerson will be playing one of at least two main threats to Oliver Queen, another being Fringe alum Kirk Acevedo’s Ricardo Diaz (who is inspired by DC Comics’ Richard Dragon).

“This character that we’re having [Michael] play is somewhat similar to people has has played in the past,” Mericle shared. “But we had many conversations with him about how to make it different, and what elements we could bring to the character to change it up.”

On The Practice (where future Arrow co-showrunner Marc Guggenheim first met the actor), Emerson won his first Emmy Award for guest-starring as serial killer William Hinks. It was during Season 2 of Lost that he debuted as enigmatic puppet master Benjamin Linus, while on Person of Interest he starred as the extreeeeemly computer-savvy (Cayden James-like?) Harold Finch.

Whatever Emerson is now up to on Arrow, the bosses are loving what they’re seeing. “He is a dream to work with, and I think he’s doing an amazing job,” raves Mericle. “We’ve seen some dailies of some of his episodes and he’s just fantastic. He’s a really understated, subtle actor, and that brings a different energy on set. It’s great.”

VIDEO: Watch the Surprised Arrow Cast React

in Real-Time to the Michael Emerson News