Based on a series of novels called "Enola Holmes Mysteries" by author Nancy Springer, the "Stranger Things" actor will star as Enola, the much younger sister of famed detective Sherlock Holmes and Mycroft Holmes, reported Deadline.
In the series, Sherlock is already a famed detective while Enola, 20 years younger, is still at home being raised by their mother. That is until mom suddenly disappears, and it's left to young Enola to solve the mystery.
Brown will also produce through her PCMA Productions banner, while Alex Garcia and Ali Mendes will oversee the project for Legendary Entertainment.