Kiefer Sutherland on returning to Jack Bauer in "24: Live Another Day"

Kiefer Sutherland as Jack Bauer in "24: Live Another Day."

Kiefer Sutherland is reprising his role as Jack Bauer for an abbreviated version of the "24" format, called "Live Another Day," and the action star dished to ET Canada about the decision to come back.

"I said yes very quickly and then went through about six months of panic," said Sutherland, who was concerned about how the return would live up to the body of work they'd already created. "I was very nervous about starting again."

"Live Another Day" sees Jack in London, as he's been in exile for four years.

"I think he's colder and, therefore, more frightening," said Sutherland. "He's different. He's someone who you might not be able to trust to do the right thing."

The 12-part series premieres May 5 on Fox.