Ewan McGregor taking on the role of Danny Torrance.
Doctor Sleep picks up several decades after The Shining, with Dan Torrance still scarred by the events of the Overlook Hotel, but attempting to put his life back together when he encounters a young girl who also possesses the strange power called the shining. Flanagan has gone to great lengths to recreate elements of Stanley Kubrick's horror classic for Doctor Sleep, but he's deviating from it in some big ways too, including the return of Hallorann.
In both the novel and movie versions of The Shining, Hallorann works at the Overlook Hotel and meets with Danny, teaching him about the shining, which he also possesses. Where the two differ, however, is in Hallorann's ultimate fate. In Stephen King's novel, Hallorann is attacked by Jack Torrance with a croquet mallet, but manages to survive and eventually helps Danny and Wendy escape from the Overlook Hotel just in time. In Kubrick's The Shining, although Halloraan initially starts out the same, his ending is very different. He arrives at the Overlook Hotel to help Danny and Wendy escape, just like in the book, but Jack attacks him with an ax and he dies as a result.
Doctor Sleep is a sequel to King's The Shining in of its narrative, although its a cinematic/visual sequel to the movie. Because Hallorann survived The Shining book, and appears in the Doctor Sleep novel, then that's how the "dead" character can return in the Doctor Sleep movie without necessarily being a direct retcon of The Shining film. Since Hallorann has the shining and a relationship with Danny, it's likely he'll have an important part to play in Doctor Sleep.
In The Shining movie, Hallorann was played by Scatman Crothers, and the role in Doctor Sleep is being filled by Carl Lumbly. It's unclear exactly where life will have taken Hallorann in the years since The Shining, and that's something Doctor Sleep will no doubt explore in some capacity, but at the very least it's a lot different to how it turned out in the original movie, since this time he's actually still alive. Doctor Sleep is scheduled for worldwide release on October 30, 2019, and in the U.S. and Canada on November 8, 2019.
