It has been seven hours since Roland awakened to find the man in black dead beside him. Roland is on a beach, where he’s attacked by a 4-foot long, shelled creature he refers to as a lobstrosity. The monster bites off two of his fingers and a big toe, leaving him in severe agony. As he weakly walks down the beach, he wonders if he has come to the end of his quest for the Dark Tower and the answers about life and death he’s been seeking.
He feels infection spreading through his body and knows it will soon reach his heart. Just when he thinks he can go no further, he finds a strange door on the beach. Entering it, he finds himself in the body of a man named Eddie Dean. Roland doesn’t know the man’s name, but he recognizes him as “The Prisoner,” about whom he’d been warned by an oracle in the previous book. The oracle said that three was the number of Roland’s fate. “The Prisoner,” a heroin addict, was one of the three individuals with whom Roland would have to contend.
Roland, a gunslinger from another world or time period, finds himself on an airplane. He is looking out through Eddie’s eyes and seeing Eddie’s world. He has the ability to watch from deep within Eddie or step forward and essentially control the man. Eddie’s greatest concern is how he will pass through customs and not get caught with the cocaine taped on his skin below his armpits. He’s smuggling the drugs for a kingpin named Balazar.
An attentive stewardess recognizes Eddie’s strange behavior and alerts the captain as they land. Roland realizes his own body, still languishing back on the beach outside the door, will not survive without medicine of some kind. If his host knows a man who deals in drugs, surely that man can help him get the medicine he needs. Roland tests a theory and discovers he can take items back outside the door to the beach and bring them back to Eddie’s world. He makes a plan to take the drugs from Eddie’s body into his own world long enough for Eddie to get through customs. But he realizes he must make contact with Eddie to do this.
After Eddie overcomes his initial concern that he’s hearing voices, he follows Roland’s instructions. When the flight has landed, Eddie removes the drugs in the airplane bathroom while pilots in the hall demand he open the door. The transfer of the drugs to Roland’s world is successful, and Eddie is smug as frustrated customs officers find nothing illegal on him.
After Eddie leaves the airport, he’s picked up by one of Balazar’s henchmen. Balazar has drugged and kidnapped Eddie’s addict brother, Henry, in an effort to ensure Eddie doesn’t run off with the drugs he’s smuggled. Balazar’s sources have told him that Eddie was detained by customs, but the amount of time he spent there makes Balazar wonder how Eddie was allowed to leave with the drugs.
Eddie assures Balazar he has them, that he simply needs to go into Balazar’s bathroom and he will bring them out. Balazar has one of his men check the bathroom to make sure it’s clear. Then he makes Eddie strip naked. Balazar tells his man to go into the bathroom with Eddie. Eddie goes into the bathroom and steps back through the door to the beach.
The confused henchman is eaten by lobstrosities. Eddie and Roland come out of the bathroom shooting. A bloody gun battle ends with Balazar and all of his men dead. Before being shot, one henchman brings Henry’s severed head to Eddie. Eddie is overcome with grief. Roland invites him to come back through the door into his world. Eddie agrees, since he feels he has nothing left in his own world.
The next weeks are a blur as Eddie detoxes from his addiction and Roland’s body heals, thanks to antibiotics from Balazar’s medicine cabinet. Much of the time, Roland is weak or unconscious, and Eddie pulls Roland’s body along when they travel. Eddie discovers that the lobstrosities are good for food, and he shoots them to keep himself and Roland alive. When Roland is finally back on his feet, he and Eddie travel until they find a second door into another world.
Now in 1959, Roland is looking through the eyes of “The Lady of Shadows,” a black woman with two personalities. As Odetta Holmes, she is a wealthy, well-dressed heiress living in a building full of white people. When she is Detta Walker, she is an extremely crass, lowbrow woman.
This woman is also an amputee, whose legs were severed some years earlier when she was pushed in front of a subway train. When Roland finds her, she is Detta. She’s shoplifting at Macy’s and about to be caught by security. Roland wheels her, kicking and screaming, back into his world.
When the woman awakens in Roland’s land, she is the kind, well-spoken Odetta. Eddie speaks with her for a while and falls in love almost immediately. Before long, she returns to being Detta. The three continue their interminable journey along the beach in search of the next door. To Eddie’s and Roland’s dismay, Odetta does not reappear. They’re finally forced to tie the fighting, cursing, obscene Detta to her wheelchair.
Sometimes Detta screams at night simply to prevent them from getting any sleep. Roland’s infection flares up again, and their supply of ammunition for hunting lobstrosities begins to run out. The weakened Roland sends Eddie and Detta on ahead to search for the third door.
During this span of a few days, Odetta reappears. Eddie’s love is rekindled. When they reach the door, they spend the evening wishing on a star and having sex. The next day, as he prepares to take the chair back and get Roland, he gives Odetta a gun. Roland has vehemently warned him against this, as they don’t know when Detta may resurface. But Eddie can’t stand to leave Odetta defenseless while he’s away.
Eddie goes back for Roland, who is angry when he learns that the woman is armed. When the two men reach the door, there is no sign of the woman. Roland urges Eddie to go through the third door with him, but Eddie will not leave his love behind. Roland goes through the third door alone.
Roland finds himself looking through the eyes of “The Pusher,” an accountant named Jack Mort who gets sexually aroused by hurting people. Roland arrives just in time to keep Mort from pushing Jake, Roland’s young friend from the previous book, into the street to his death. Mort then hides in an old building and tosses a brick down to hit a young black girl. It is Odetta, and this was the injury that put her in the hospital with a concussion as a child. He also realizes Mort is the same person who pushes Odetta in front of a subway train years later.
Roland is infuriated by Mort. He quickly realizes he hasn’t been sent to this time and place to locate another traveling companion, but to destroy this evil man. Roland uses Mort’s body to get ammunition for his gun and medicine for his infection.
Meanwhile, on the other side of the door, Detta has resurfaced. She has tied Eddie in multiple ropes and left him in the ocean. Both know that if Roland doesn’t return by sunset, the lobstrosities will destroy Eddie. Detta waits at the door with Roland’s gun, intending to attack Roland when he returns. Roland looks through the door, making eye contact with Odetta and Detta simultaneously, before pushing Mort in front a of a subway train. The sight jars something in the woman.
Still, she is waiting for Roland with a gun when he rushes back into his world and attempts to save Eddie from the swarm of lobstrosities. Suddenly, Detta turns her gun and her wrath on the lobstrosities and saves Roland and Eddie from certain death in the sea. Afterward, in her right mind, she says she is three women: the woman she was, the woman she had no right to be but was, and the woman Roland saved. She takes the new name Susannah Dean.
Roland continues to heal using the antibiotics he took from Mort’s world. As the three travel on, Eddie is concerned. He knows Roland’s quest means more to him than anything and anyone’s life, including his and Susannah’s. He asks Roland if the Gunslinger will let them die, if that is necessary to complete his quest. Roland does not deny it. Roland sleeps and continues to dream of the Tower.