In the year 2045, Wade Watts won a contest. The contest was held in the OASIS, a virtual galaxy where users log in and experience many worlds dedicated to music, movies, books, games, education, and many other facets of pop culture. The real world is in ruins. Climate change, famine, war, and overcrowding have destroyed most nations. The OASIS is the only refuge for many people. When Wade won the contest, he received controlling shares in the OASIS, valued at hundreds of billions of dollars. He split the controlling shares with his three friends, Aech, Shoto, and Art3mis (Samantha).
Immediately after the events of the first book, Ready Player One, Wade is given a secret message that leads him to find a new technology. The ONI, a new headset that interfaces with the user’s brain, allows people to log on to the OASIS and experience all its various locations and activities with all their senses. Wade knows that it will change the world. He and his friends, Aech and Shoto, believe that it should be released. Samantha thinks that it is too dangerous. Wade releases it and he and Samantha break up.
A new contest appears in the OASIS, instructing users to find the Seven Shards of the Siren’s Soul. Wade is unable to find a single shard for several years and eventually offers a billion-dollar prize to anyone who can help him find one. A gunter named L0hengrin contacts Wade and tells him that she can help him find the First Shard. L0hengrin shows Wade how to acquire the First Shard. The shard causes Wade to have a flashback where he is Kira Underwood, Ogden Morrow’s wife. The shard also contains another clue, but Wade pays and dismisses L0hengrin before she can give her input.
In the same meeting, Wade finds out that Ogden Morrow, the remaining co-creator of the OASIS, has gone missing. Nolan Sorrento, the leader of the villainous Sixers (that Wade faced in the previous book) escapes from prison. Wade assumes the two events are related. He then finds out that Ogden Morrow has found several of the shards. Wade is called to an urgent meeting. At the meeting, Anorak tricks Wade into giving up his super-user access. Anorak was James Halliday’s avatar but is now a functioning AI, made from a brain map of the deceased Halliday. Anorak tells Wade, Aech, Shoto, and Art3mis that he can keep them all logged in to their ONI units until it kills them, unless they find the Siren’s Soul Shards for him. Anorak also has Ogden Morrow—who was collecting the shards, but stopped cooperating—as a hostage.
Art3mis does not use an ONI rig and logs out to work on a separate agenda. Wade, Aech, and Shoto try to locate the shards. They acquire the Second Shard in a version of Ninja Princess, and Wade has another flashback where he is Kira Morrow. Wade starts to wonder how Halliday could have programmed accurate flashbacks to events where he was not present. The group wonders if Halliday created a digital copy of Kira Morrow’s brain sometime before she died.
The Third Shard is located on the planet Shermer, Illinois, dedicated to John Hughes’s movies. Art3mis leads Wade, Aech, and Shoto through several different locations. Art3mis and Wade are able to change the ending of Pretty in Pink and obtain the Third Shard, which gives Wade another Kira flashback. The next clue leads them to Halcydonia, a planet made of educational games. Wade spent most of his childhood there and navigates it easily. Wade receives the Fourth Shard and experiences another flashback.
Wade, Aech, Shoto, and Art3mis figure out where Anorak is keeping Ogden Morrow. Art3mis logs out to help rescue him in the real world. The next stop for the remaining group members is a planet dedicated to the rock star Prince. Aech is a huge Prince fan and guides Wade and Shoto through many different locations, preparing to battle several versions of Prince at the same time. Shoto’s avatar is killed in the battle, but Aech and Wade are victorious, winning the Fifth Shard.
The clue on the Fifth Shard leads Wade and Aech to Arda I in search of Morgoth, one of the original villains in the universe of Tolkien’s stories. Aech’s avatar is defeated by a large wolf and Wade is saved by Art3mis. Art3mis is a Tolkien expert and helps Wade retrieve the Sixth Shard. Wade teleports to a shrine dedicated to Kira Morrow and places the six shards, receiving the final shard. Anorak appears and demands the completed Siren’s Soul. Wade combines seven counterfeit shards and tricks Anorak into giving up his magical robes. Wade teleports back to the room with the Big Red Button and threatens to destroy the entire OASIS, along with Halliday.
In the real world, Ogden Morrow is rescued and logs back in to fight Anorak. After Anorak is defeated, Ogden Morrow dies. Wade combines the Seven Shards and meets the AI copy of Kira Morrow that Halliday created. She gives Wade the power to create AI copies of anyone who has ever used an ONI headset. Wade creates a copy of Ogden Morrow for her.
The epilogue describes how digital AI copies of Wade, Samantha, Aech, Shoto, Ogden, and Kira are traveling on a spaceship that Wade commissioned. They travel into deep space to find another planet for humans to inhabit.