(Please note that this is not a stand-alone book, but rather a sequel to Fortress of Thorns.)

The Grey Man can be thwarted and frustrated -- but not for long. At the beginning of The Grey Road, he's been quiet for several months after the end of Fortress of Thorns. Charlotte figures that means he's got something planned, and she comes up with some plans of her own. She's been developing her ability to use magic in her home world, and Miri and Nate have been working with her. They've drawn together a circle of their friends from school into a team of magic users who can stand up to all the powers of the other place. With a little help from Charlotte's magic, Sam and his brother Nicholas move to town, too. Only Megan is left out.

When one of the Grey Man's minions tries to kill Nate, the battle is truly started. The festival of Tournament is upon them, and the Grey Man makes a bid for power recognition in the Tournament among the other Powers. To appease him without giving him everything he wants, Nate fights an exhibition match with the Grey Knight. He wins, but at the very end, the Grey Man pulls the Grey Knight out of the ring, breaking all the rules and forfeiting the match. And Nate feels something very peculiar....

Charlotte is focused on figuring out how to destroy the Grey Man. Just beating him isn't enough. She wants him to be gone from the other place, forever, with no successors. Coyote turns her on to the Labyrinth to get answers no human being can provide. The Labyrinth oracle will answer one question for each person who makes it to the center of the Labyrinth -- but only some of the group can do it without being thrown back to their homeworld by traps or by the human guardians of the Labyrinth. And the information Charlotte gets is inconclusive.

In the meantime, Miri is trying to keep the group together, while Megan gets sick of being the only one who can't do magic -- and tired of lying for Nate about his gifts. Charlotte comes close to losing Miri's friendship when Charlotte's practice in making magic traps to catch the Grey Man backfires on Nate and Miri. Charlotte is trying to do what the Gray Man does to his victims: trapping them in their own negative emotions. In Charlotte's trap, Nate has to relive the day his dad died, and Miri has to relive the day that Charlotte became the Grey Man's prisoner.

When Charlotte manages to break the spell she accidentally put on them, Miri and Nate are furious with her. They stop speaking to her and move on with their own plans to thwart the Grey Man. Miri goes through a ritual that gives her the Moon Mother's power back without taking away her powers as the Wanderer. Miri knows that this choice implies that she will later become the Moon Mother and not the Queen of Roads, but it's a choice she's willing to live with. The Queen of Roads is disappointed to lose her, but she claims not to be angry.

Sam gets frustrated with Nicholas for throwing himself so wholeheartedly into the new group of friends and the other place; he's afraid they'll get caught. Megan is only speaking to Nate when their mother requires it, and Charlotte's parents are angry with her for her self-centered behavior. Time in the other place provides no respite from conflicts at home. Before Nate's recital, Charlotte tries to mend her relationships with her parents and with Miri; Megan feels like her brother needs her support while he plays. Not everything is perfect, but they work their way to a shaky peace. Miri, however, is the one who reaches out to bring Megan back into the group despite her lack of magic powers.

Everyone except Nicholas agrees that Charlotte should not do any more trap spells. They are too dangerous; they are what led the Grey Man astray. Charlotte does not agree but promises the rest of the group that she won't make any more traps unless they decide there's no other way. Nate has figured out that he shares a bond with the Grey Knight from when the Grey Knight was the Green Knight. Through this bond, he may be able to affect the Grey Man. But when the Thorn King will not let him use all of his power to defeat the Grey Man, the opportunity slips through his fingers.

In frustration, the group rallies around a multi-part plan, where some people will deal with the Grey Man in his home and others in the other place. The other powers refuse to directly aid their group, so a rag-tag group of people led by Coyote join the teenagers to take on their world's greatest evil directly. Nate even makes amends with the Baker, who agrees to help them out in their battle with the Grey Man. Nate and Miri create a stockpile of magical energy they can use to bind the Grey Man to the other place while the others batter him with their battle spells.

Coyote's group is struck down before they can even start -- a traitor among them must have told the Grey Man's forces where and when they would meet, but no one can say who it was. Nate and Miri, in our world, manage to bind the Grey Man to the other place, but Charlotte and Nicholas' group is forced away from the other place one by one as they try to take back the Grey Place. When it is only Charlotte and Nicholas left, they know what they have to do. Each of them creates a trap for the Grey Man. At the last minute, Nicholas pushes the Grey Man away from Charlotte's trap and into his own. But in their moment of victory, Charlotte faces a worse horror: Nicholas himself has become the Grey Man. Shocked, she runs away from him and refuses to talk to him. The rest of the group can see his behavior change, a little at a time.

To finish off the old Grey Man's regime, Nate decides he must take on the Grey Knight. Before he pulls the older man into a duel, he talks things out with his sister and tries to explain the other place to his mother. Although he has limited success, he can face the Grey Knight with a clear conscience -- which is shaken when he must kill him. The group is left shaken and dismayed, with all of their good goals achieved in the worst and most difficult way they can think of.