In a vast multiverse containing various parallel worlds, a mythical structure known as the Dark Tower stands at the nexus, maintaining the balance of the cosmos. The dark sorcerer Walter o'Dim, also known as the Man in Black, seeks to collapse the tower and unleash chaos across the universes by torturing psychic children whose "shine" possesses the power to destroy the tower. Opposing him is Roland Deschain, the last of the Gunslingers, a group of elite warriors dedicated to protecting the tower. Roland is driven by a quest for vengeance against the Man in Black, who is responsible for the downfall of his world and the deaths of his loved ones.

In modern-day New York City, a young boy named Jake Chambers experiences haunting visions of the Dark Tower, the Man in Black, and Roland. His dreams, dismissed as troubled fantasies by those around him, propel him on a quest to find the truth. His search leads him through a portal to Mid-World, where he encounters Roland. Despite Roland's initial indifference to the tower's fate, Jake's conviction and unique abilities persuade him to join forces with the Gunslinger. Together, they journey through desolate landscapes, battling the Man in Black's minions, as they seek to protect the tower and save the universes from destruction.