He told SFX that Becoming Human will be aimed at a younger audience than its parent series.
"We had this idea to set it in a school," he explained. "It's about these kids in detention [so] you could call it a supernatural Breakfast Club!"
The seven-part web series will focus on the circumstances surrounding the death of the ghostly Matt (Josh Brown).
"The story's about establishing the causes of Matt's death so he can complete his journey," Whithouse confirmed. "Every day the site will be updated in some way, so more clues will gradually filter out. It makes it much more enjoyable, because rather than just being a spectator, you're much more of a participant."
The writer also revealed that the series will refer back to the original Being Human.
"It's set in a different part of the country, one that's undefined, but takes place in the same world," he said. "We have the same rules and there are references to characters in the main show."
Being Human returns to BBC Three in late January. Becoming Human will launch online following the second episode.