Sherlock creator Steven Moffat has described Benedict Cumberbatch's new nemesis, Charles Augustus Magnusson, as "terrifying".
The Killing star Lars Mikkelsen has taken on the role of adversary in series 3 of the BBC detective drama.
His character has been loosely based on Sir Arthur Conan Doyle's 'king of blackmailers' Charles Augustus Milverton.
In the original short story, Milverton extorts money from his victims by using the threat of scandalous revelations.
And while Steven would not reveal to what extent Lars' character will echo the original, he confirmed to the Radio Times, "Lars is terrifying".
"We've drawn from that story, but, as ever with our show, what we drew, and how we do it and how we find equivalences, (you'll have to wait and see)," he teased.
"Sometimes, as you know, we flip things and make them the other way round. We do all those things.
"I'm not giving away what we've done with him but I think we've done something good… You'll know the angle we've taken on it within seconds of it beginning."
Benedict Cumberbatch and Martin Freeman — John Watson — are expected to return to BBC1 in Sherlock in late 2013 or early 2014, when the mystery of the detective's death-defying plunge from a roof will finally be explained.