Oliver Platt didn’t quite realize what he was getting into when he took on playing Paul Jamison, the boyish, clueless husband in the Showtime dramedy “The Big C.”

His onscreen wife, Cathy (Laura Linney), keeps her terminal cancer diagnosis a secret from him, and the two are left to figure how to proceed from there.

“I loved the premise but it turned out to be really hard to react to circumstances where the character is in the dark but I, the actor, know what’s going on,” Platt says. “The challenge is to do it honestly, without calibrating. You go, ‘Forget about what you know.’ ”

What Platt finds easy about the job is working with Linney. The two were in the 2004 film “Kinsey” and struck up a friendship.

“Cathy and Paul are really different from each other. Laura and I work in different ways, yet there are ways that we work that are incredibly similar,” Platt says. “Neither of us likes to talk about it too much, or rehearse too much. We like to see what happens in front of the camera. We have respect for the mysteriousness of the process.”

In season one, the two do a complicated emotional dance of love, confusion and pain often fueled by Cathy’s unpredictable behavior — from throwing Paul out of the house to sleeping with another man.

“It was frustrating for Paul, and in a bizarre way it became frustrating for me,” Platt says. “I had good old-fashioned actor-character confusion. You overidentify with the person you’re playing. For me, that’s an incredibly healthy, free thing, when it comes to the acting.”

Supporting drama actor race wide open| Shows elevate when ensembles gel
Peter Dinklage | Michelle Forbes | Irrfan Khan | “The Killing” cast | Kelly Macdonald | Margo Martindale | Denis O’Hare | Amy Ryan | Michael Shannon | Donnie Wahlberg |

Mayim Bialik | Garret Dillahunt | Oliver Platt | Adam Scott