After a quiet 2014, Leonardo DiCaprio will return to the big screen with this year’s The Revenant, from Oscar winner Alejandro González Iñárritu. The actor will also begin development on a project he’s been wanting to do for close to twenty years: the true story of Billy Milligan, the first man to successfully use a multiple personality disorder defense in a court of law. The film, titled The Crowded Room, will be produced by DiCaprio’s production company Appian Way, along with New Regency, THR reports.

DiCaprio is said to have wanted to do the project since as far back as 1997, and while the film has been in place at New Regency for a decade, it’s never even been close to getting the green-light until now. With DiCaprio starring and producing alongside Jennifer Davisson and Alexandra Milchan, scribes Jason Smilovic (Lucky Number Slevin) and Todd Katzberg have been hired to adapt Daniel Keyes’ 1981 book The Minds of Billy Milligan.

Milligan’s story is one primed for the Hollywoood treatment. Milligan, who had committed several felonies (including armed robbery), was arrested for three rapes on the Ohio State University campus. In the process of preparing his defense, psychologists determined that Milligan had multiple personality disorder. One of those personalities, a lesbian named Adalana, took responsibility for the rapes while another – a Yugoslavian communist named Ragen – claimed the armed robberies. Altogether Milligan, who died in December of last year, is said to have had 24 different personalities.