The Gunslinger

As Roland travels across the desert in search of the man in black, whom he knows as Walter, he encounters a farmer named Brown and his raven, Zoltan. Roland spends the night there and recalls his time spent in Tull, a small town Roland passed through not long before meeting them. The man in black had also stayed in the town; he brought a dead man stricken by addiction to the opiate-like "devil grass" back to life and left a trap for Roland. Roland meets the leader of the local church, who reveals to him that the man in black impregnated her with a demon. She turns the entire town against Roland, who is forced to kill everyone. When he awakens the morning after telling Brown the story, his mule is dead, forcing him to continue on foot.
Roland arrives at an abandoned way station and first encounters Jake Chambers, a young boy. Roland collapses from dehydration, and Jake brings him water. Jake remembers neither how long he has been at the way station nor exactly how he got there, and he hid when the man in black passed through. Roland hypnotizes Jake to determine the details of where he came from and discovers he died in a different universe that appears much closer in nature to our own. He was pushed in front of a car while walking to school in Manhattan. Before they leave, Roland and Jake search for food in a cellar and encounter a demon, which uses a skeleton entombed behind a wall to speak to them. Roland masters the demon and takes the skeleton's jawbone.
Roland and Jake make their way out of the desert. Roland rescues Jake from an encounter with a succubus and gives him the jawbone to use as a protective charm against it. Roland leaves him at camp and couples with the succubus, who is also an oracle, to learn more about his fate and the path to the Dark Tower. In a flashback, it is revealed that Roland is the son of Steven Deschain, a Gunslinger and lord of Gilead. Roland received brutal training at the hands of his teacher, Cort. Roland was tricked into a premature test of manhood by dueling with Cort at age 14, earlier than any other apprentice. He was provoked by Marten, who served as Steven's wizard and seduced Roland's mother, Gabrielle. That was a time of instability and revolution. Roland defeated Cort in battle by choosing his hawk, David, as his weapon and sacrificing him to distract Cort.
Jake and Roland see the man in black at the mountain. He says that only he and Roland will meet on the other side, exacerbating Jake's fears that Roland will either kill or abandon him. Roland and Jake make their way into twisting tunnels within the mountain, traveling on an old railway handcar. They are attacked by subterranean creatures called "Slow Mutants." At the tunnel's exit, they continue on foot. As the track on which they are traveling begins to break, Roland lets Jake fall into an abyss and continues his quest.
After sacrificing Jake in the mountain, Roland makes his way down to speak with the man in black. The man in black reads Roland's fate from a pack of cards that includes omens such as "the sailor," "the prisoner," "the lady of shadows," "death," and the Tower itself. The man in black states that he is a pawn of Roland's true enemy, who now controls the Dark Tower itself. The man in black also reveals that he was Marten. He then sends Roland a vision of the universe, zooming out past a red planet covered in canals, a ring of rocks, a large stormy planet, a ringed planet, and then to galaxies and beyond, attempting to frighten Roland by showing him how truly insignificant he is. The man in black then asks Roland to renounce his quest. Roland refuses, and the man in black tells him to go west before putting him to sleep. When Roland awakens, 10 years have passed, and there is a skeleton next to him that he assumes to be the man in black. Roland takes the jawbone from the skeleton, as a replacement for the one he gave to Jake, before traveling to the shore of the Western Sea.