Whitechapel star Phil Davis will appear in the drama's fifth series as the "manipulative... and cruel" Captain Hatch.
"In episode one there's a scene that puts a full stop on the Old Ones, and we move on to much bigger and greater threats," Whithouse told SFX.
The writer went on to describe the character of Hatch as "gloriously horrible", praising the "brilliant" Davis.
"I can't tell you how happy I was when we got Phil," he said. "I was writing the first draft of episode six, which is a colossal episode for the character, and I was struggling to find the character's voice; something about it wasn't clicking.
"Then I thought, 'Oh, y'know who'd be brilliant for this part? Phil Davis'. Suddenly, writing that character became infinitely easier."
> The Fades axed in favour of Being Human, says writer Jack Thorne
> Being Human Toby Whithouse: 'Series five is great opportunity
Being Human will return to BBC Three with six new episodes in 2013, with Kate Bracken joining the regular cast as new ghost Alex.
Watch a clip from the last series of Being Human below: