The first trailer of The Dark Tower tells you about a boy, Jake, who ventures to another world where he meets the gunslinger Roland Deschain, a man he has been seeing in visions. Gunslingers are the former knights of the other realm tasked to fight the darkness but when there civilization was ruined by the Man in Black, Walter O’Dim, the gunslingers became wandering souls without purpose. Deschain took it upon himself to find the dark tower to preserve his dying world.

The dark tower is a seal that protects both earth and the Deschain’s realm from the creatures of darkness. One world has fallen in ruin and now the gunslinger must to take up arms once more to save the boy’s world from destruction.