On Thursday, December 12, Michael Emerson opens a recurring arc ElsbethHe plays an unexpected adversary alongside his wife Carrie Preston, who plays the titular lawyer who continues to help the New York Police Department solve various murders Good woman Spin off.

Before his debut as Judge Milton Crawford, the former Lost Star, 70, and Preston, 57, spoke to PEOPLE about what to expect from his character and what it’s like for the longtime couple to go from loving spouses at home to fighting with each other on set.

“It’s interesting, strange and complicated,” Emerson says of working with Preston, particularly on the CBS trial, in which they are at odds after Elsbeth interferes in a murder trial that Milton is presiding over. (See above for PEOPLE’s exclusive preview of Emerson’s debut episode, which hints at the growing tension between Milton and Elsbeth.)

He adds: “It’s like a double-shift acting day. You have to pretend you don’t know the person you woke up with in the morning and treat them as if they were a fictional character and not like your opponent.” Your spouse. So there’s a lot going on while a lot is opening.

Unlike the series’ previous guest stars, who appear as various suspects and criminals in one episode, Emerson will have several episodes to get under Elsbeth’s skin as Milton and “unhinge her a little,” Preston teases adding: “It’s really fun to have a Moriarty as my Sherlock, you know, this character that she can’t understand, that’s a thorn in her side.”

Emerson, for his part, says his character is “an ongoing problem for Elsbeth” and jokes that he’ll be curious to see who will win this clash when they’re “likely to clash again soon.”

Preston adds, “It’s just fun to play these different dynamics.”

The couple first met in 1994 before marrying in 1998. Now, 26 years after their marriage, Preston says: “We have a really lovely time together. We make life very good together. We kind of balance each other out.”

And although the two don’t appear on screen together that often – Elsbeth marks the second notable time they shared scenes on each other’s show after Preston had a recurring role Person of interestin which Emerson starred as a billionaire computer programmer – she says: “We kind of had that balance on set too.”

Filming Emerson’s storyline also provided the two, both of whom are usually busy with their own shows, in which Emerson most recently starred Devilish and appears in season 1 of Stand out – with the unexpected chance to spend valuable time together.

“We recently did a scene together when we were filming in Harlem, and we had a little break,” Preston recalls of filming Elsbeth in Manhattan, where the series takes place. “The caravans were far away, so we just took a little walk together and held hands.”

She adds: “Normally I would then call him or text him. But that wasn’t necessary. He was just there and that was nice. It was a beautiful little moment where I thought, ‘Oh, this is’ ‘It’s so nice that I can just come up to you and hold your hand without us having to communicate in any other way.'”

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Elsbeth airs Thursdays at 10 p.m. ET on CBS.