Benedict Cumberbatch, star of PBS skein “Sherlock,” is set to join the cast of New Regency’s “12 Years a Slave.”

Steve McQueen is directing the pic starring Chiwetel Ejiofor, Michael Fassbender and Brad Pitt.

Based on Solomon Northrup’s 1853 nonfiction tome, New Regency pic stars Ejiofor as the author, a free man kidnapped and sold into slavery. Cumberbatch will play a plantation owner who buys Ejiofor’s character and is won over by his engineering skills.

McQueen co-wrote the script with John Ridley (“Red Tails”). Dede Gardner and Jeremy Kleiner will produce for Plan B.

Production will start at the end of June, and CAA is arranging financing for the pic in addition to repping its U.S. rights.

Cumberbatch, repped by UTA and Conway Van Gelder Grant, has broken out recently in film with strong roles in Paramount’s “Star Trek 2,” Peter Jackson’s “The Hobbit: An Unexpected Journey” and HBO’s “Parades End.”