Hardin will play Isabella Stone, who is described as "a socialite by day, character assassin by night." Stone is a Blacklister who is ruthless when it comes to taking out targets and uses methods including scandal, public humiliation, extortion and theft.
The actress played Tammy Cashman in the first two seasons of Amazon's critically acclaimed drama Transparent. She is probably best known for her tenure as Michael Scott's (Steve Carrell) on-again-off-again love interest Jan Levinson on The Office.
Hardin's appearance will be in the Feb. 9 episode directed by Andrew McCarthy. The episode airs two weeks before The Blacklist spinoff The Blacklist: Redemption kicks off on Feb. 23, which will see Tom Keen (Ryan Eggold) joining his mother (Famke Janssen) on a highly trained team of black ops professionals.
The Blacklist airs Thursdays at 10/9c on NBC.