Best known for playing mayoral candidate Troels Hartmann in the original Scandinavian version of the TV series "The Killing," Mikkelsen will play Charles Augustus Magnussen on "Sherlock."
The BBC said the title character in Arthur Conan Doyle's "The Adventure of Charles Augustus Milverton" was a blackmailer who extorts money from wealthy nobles.
"Sherlock" is a contemporary re-telling of Doyle's 19th century Sherlock Holmes detective stories.
Benedict Cumberbatch plays Sherlock on the critically acclaimed show.
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