The complexities of “Awake” — a drama about a cop who alternates between two dream realities after a car crash: one where his wife survived; the other, his son — weren’t lost on Jason Isaacs.

“I was in my head in every single moment, and not just existing and reacting to it, but asking myself why my character might be creating this,” Isaacs says. “If I ever looked like I needed a coffee, or had too many vodkas for breakfast, it was because I had a whole universe in my head on screen.”

Isaacs realizes the character had a lot on his mind; he solved cases in both realities, with clues from one often encroaching into the other. Not to mention consoling his wife as she mourns her son, and vice versa.

Isaacs, naturally, approached the role delicately.

“This couldn’t be a show about some guy that was miserable in both worlds,” Isaacs says. “This guy had a second chance in both worlds. I had to treat each with equal respect, and have both be real.”

“Awake,” despite early ratings traction, saw a viewer fall-off and wasn’t renewed for a second season. But it was fascinating while it lasted, and gripped Isaacs from the moment he picked up the pilot script.

“I didn’t know what would happen next,” he recalls. “With most films, plays and TV dramas I’ve done, you know the story. All we had here was a fantastic beginning. I was desperate to find out what happened next and how to play it.”