Whereas The Gunslinger Born was largely based on the events of The Dark Tower IV: Wizard and Glass, Treachery, like The Long Road Home, consists mostly of new material not found in any of the novels.
The story depicts the ka-tet of Roland Deschain, Alain Johns and Cuthbert Allgood dealing with the events following their return to Gilead from Hambry, including the toll that Maerlyn’s Grapefruit has taken on Roland’s health, his obsessive desire to continue peering into its depths, and the search for John Farson and the Big Coffin Hunters.
EHT Comics 