In the prologue, two BloodClan cats, Snake and Gremlin, spy on Firestar and Sandstorm as they leave their territory. They report back to their leader, Fury, and BloodClan knows that their time for revenge is near now that Firestar is out of the way and ThunderClan is weakened. Gremlin worries about what will happen to the kits she’s carrying if she has to fight.
After the events of Veil of Shadows, Graystripe feels that the Clan is falling apart. He promises Squirrelflight that he'll do his best to help her keep them together, but several of the cats consider leaving for a while. Graystripe questions his own role in the Clan, since the younger cats don't want to listen to him, and ultimately he decides to leave too. He starts off with the other cats who wanted to leave, and then concludes that he needs to look back on his past to shape his future, deciding that he'll go visit Stormfur and the Tribe. Of the cats who'd left ThunderClan, Thornclaw goes off on his own, Flywhisker and her brother Snaptooth decide to stay closer to Clan territory, and Flipclaw joins Graystripe on his trip to the mountains.
In the past, while Firestar's gone on his quest, Graystripe struggles to keep ThunderClan in order; some of them aren’t respecting his authority as acting leader. There seems to be evidence that WindClan's stealing prey, but something doesn’t seem right, and Graystripe is reluctant to take action. ShadowClan brings news that BloodClan's been scented recently, and soon BloodClan themselves attack one of Graystripe's patrols. He realizes that they'd disguised their scents by using the WindClan border marks. The BloodClan cats defeat Graystripe and leave him for dead, but the pregnant she-cat sees that he's alive and lets him go.
Flipclaw and Graystripe arrive at the Tribe's cave. He greets Stormfur and Brook and their kits, and Stormfur tells him that a rogue from the old forest was asking for Graystripe by name. Graystripe talks to Stoneteller, who consults with the Tribe of Endless Hunting: he sees a "shadow" in the direction of the Clans, and he knows Graystripe must continue his journey. Graystripe is reminded of the Moonstone and has a vision of Feathertail, and takes it as a sign that he must go there and see if StarClan sends him a message there. Flipclaw gets caught in a landslide but survives, and they decide that he won't go with Graystripe: Flipclaw's injury needs to heal, and he's already decided to return to ThunderClan.
Back in the past, there's been no further sign of BloodClan. Graystripe brings a patrol to WindClan and RiverClan to warn them, just in case. At the Gathering, he tells the other Clans that Firestar is recovering from greencough, and does his best to keep up the act and try not to draw too much attention to himself.
Graystripe in the present, arriving at Highstones, sees that what was once the Clans' territory is now a massive Twolegplace. He wanders around and recognizes a couple landmarks like the waterfall, but it's otherwise unrecognizable. He's confronted by a group of kittypets, who introduce themselves as "WarriorClan", led by "Monkeystar". They’d been told of the Clans by the elderly kittypet Smudge, and they did their best to be a Clan like in the stories. Graystripe, enjoying their admiration of him as a real warrior, spends the day training them, and heads toward Highstones. Along the way, he sees what once was Fourtrees, with the oaks cut down and the Great Rock crumbled to rubble.
In the past, the pregnant BloodClan cat finds Graystripe and introduces herself as Gremlin. She offers him a deal: she'll feed him information about BloodClan's plans, if he agrees to let her and her brother join ThunderClan.
In the present, Graystripe meets a cat, Fang, who has been looking for him: he tells Graystripe that Gremlin was his mother, and that Graystripe once made a vow to her that he'd do anything to help. Fang's mate and many other cats are trapped in a Twoleg nest and need his help to escape. Graystripe agrees, but first needs to go to the Moonstone. While he's there, lightning strikes the Moonstone and shatters it into rubble. Graystripe is horrified and wonders if it's a sign. WarriorClan suggests that he speak to an old wise cat they know, named Barley. Barley isn't sure what it means, but the two cats reminisce about old times and old friends.
Graystripe, as ThunderClan's acting leader, visits Gremlin and discusses her offer. He tells ThunderClan about it, and though not all cats are happy about it, they agree - at least until Firestar returns and makes a final decision. She tells Graystripe BloodClan's battle plan: in two days they'll wait until the early patrols are out and attack the camp. Graystripe listens, and decides to trust her advice.
At Barley's barn, Fang tells Graystripe about the Twoleg nest where he'd been trapped - where his mother had died. The elderly female Twoleg had started with just one cat, then took in Gremlin who gave birth to Fang and his littermates, and then seemed to grow sick: she forgot to feed the cats and herself, kept taking in more cats, became less and less capable of caring for herself, and conditions in the house grew worse and worse. Gremlin grew ill and died there. Graystripe confirms that he will help Fang. He convinces the WarriorClan cats to stay with Barley for now, and he and Fang go to the Twoleg nest. Graystripe gets inside through a window, but the Twoleg shuts it, trapping him inside. They try to get out when she goes outside, but are unsuccessful, and Graystripe wonders if he'll ever get out.
The day that BloodClan plans to attack, Graystripe prepares the Clan: he sends out patrols and training parties, ordering them to stay close to camp so that they can be reinforcements, while he has other cats hide in the dens. The battle begins. Gremlin tries to escape from the camp, but she is spotted and captured by the BloodClan cats. Her brother tries to defend her, but they kill him. Graystripe attacks Snake, but Fury tells him that if Snake dies, so does Gremlin. Graystripe notices that Fury has a bad wound on her side that she'll likely die from, and tells her that they’ll heal her if she agrees BloodClan won’t bother ThunderClan again. It takes some convincing, but eventually she agrees. ThunderClan is happy that Graystripe made the right choice and accepts him as leader. Gremlin decides that seeing the fight between ThunderClan and BloodClan, she no longer thinks that Clan life is best for her and her coming kits, and she wants to become a kittypet. As she leaves, Graystripe tells her that if she ever needs anything, to just ask.
In the present, Fang brings WarriorClan to the nest, and, from the outside, help Graystripe and the cats shift a loose floorboard. The cats all escape. As they’re sitting outside, a mailman comes to the house and notices them all, then seems to notice the smell and looks in the window before pulling something out and talking into it. More Twolegs arrive; some of them take the elderly one with them, and some are clearly trying to catch the escaping cats. Some of the older, slower cats - and Fang's sick mate Daffodil - choose to stay behind and let themselves be caught so that the younger, healthier cats can escape. Some of the cats want to go to other Twolegs, while others decide to join WarriorClan. Graystripe suggests to Monkeystar that she make Fang her deputy, and she agrees. He suggests that the Twoleg's first cat, Petunia, be WarriorClan's medicine cat since she knows a bit about healing. Graystripe knows that his time has come to leave and return to his Clan, and he's come to accept that cats can live as a Clan even without StarClan, as long as they're willing to work together and care for one another. He says farewell to WarriorClan, and on his way out of the old territory he overhears a patrol of them talking about how they should be like him. Amused and flattered, he starts to head home.
After the trouble with BloodClan ends, Firestar and Sandstorm finally return. Graystripe tells Firestar everything that happened while he was gone, and then tells him that the experience made it clear that he never would want to be Clan leader. He suggests that maybe Firestar choose a different deputy, but they ultimately decide that Graystripe will remain. Graystripe reflects on how the experience taught him that he loves ThunderClan more than anything. They go to the next Gathering with Firestar, where everyone cheers for Graystripe, and Graystripe vows privately to protect his Clan for the rest of his life.
On his way back to the Clans, Graystripe visits Barley one last time, and they say goodbye; he then goes to the Tribe and tells his son Stormfur what he'd learned and what he'd done on his adventure. Finally, he's within sight of the lake, and thinks about how he's ready to help the Clan he loves.
In the manga, Monkeystar of WarriorClan thinks about how she's learned a lot as leader. However, the Clan's medicine cat, Petunia, has been wandering off frequently and now has been gone three days, so Monkeystar leads a patrol to look for her. They find her at her old home, once again waiting for her Twoleg to someday come back. Monkeystar suggests going to the Moonstone, since Graystripe had told her it was a place to look for guidance. Even though the stone itself is broken, Petunia sees Gremlin there, who advises her to focus on her Clanmates. When they return to the rest of their Clan, Fang tells Monkeystar that clearly her idea made Petunia happy, and that he knows she'll be a fine leader.
Tropes appearing in this book:
- Afterlife Welcome: In his dream, Graystripe sees Briarlight leading Millie to StarClan.
- Battle-Interrupting Shout: In the battle in ThunderClan's camp, Fury yowls "stop!" when Graystripe is about to kill Snake, in order to show him that Gremlin will die if he does.
- Battle in the Rain: It's raining when BloodClan first attacks ThunderClan.
- Best Friend: Graystripe is Firestar's best friend, and even as an elder when Firestar is long dead he refers to him as such.
- Bring Help Back: When BloodClan attacks Graystripe's patrol, he sends Brambleclaw back to camp to bring help.
- Cave Behind the Falls: The Tribe lives in one.
- Commander Contrarian: Dustpelt remarks that Ashfur has always argued about everything.
- Continuity Nod: The flashback chapters give nods to some of the manga: the conflict with BloodClan ties in with the Ravenpaw's Path manga since its plotline previously seemed to come out of nowhere, and it also brings back Brick from the The Rise of Scourge. Graystripe also remembers some of the events of his journey to find the lake, such as the barn cats that he and Millie had met. There's also a reference to the "battle against the foxes" story from Battles of the Clans.
- Covered in Mud: The Tribe cats coat themselves in mud to help blend into the rocks.
- Crazy Cat Lady: A portion of the book involves an elderly cat hoarder. It's portrayed much more tragically than other "cat lady" instances in the series; it's strongly implied that she has Alzheimer's or a similar mental condition.
- Creepy Cave: Graystripe finds Mothermouth creepy and has to push past his fear of it to reach the Moonstone.
- A Dog Named "Cat": Monkeystar's name comes from her kittypet name, Monkey. She doesn't know what a monkey is, but she assumes that it's something fierce.
- Flashback B-Plot: The book is split into "Now" and "Then" chapters, with "Now" being the modern (The Broken Code) era where Graystripe goes back to the old territories, and "Then" being flashbacks to Graystripe's time as acting leader while Firestar was away on his quest.
- Floral Theme Naming: All of the kittypets owned by the elderly Twoleg have plant/flower names, such as Petunia, Honeysuckle, and Daffodil.
- I Will Wait for You: Millie says this to Graystripe in his dream.
- Look Both Ways: Graystripe is nearly hit on the Thunderpath by a monster when he forgets to check before crossing.
- Meaningful Rename:
- The kittypets gave themselves warrior names when they formed WarriorClan. Clawwhistle explains that he chose his for the sound of claws swiping through the air.
- Honeysuckle renamed himself Fang after escaping from the Twoleg nest.
- Name That Unfolds Like Lotus Blossom: Tribe names are like this. Especially noticeable when Stormfur and Brook are introducing their kits: Lark That Sings at Dawn, Pine That Clings to Rock, Feather of Flying Hawk, and Breeze That Rustles the Leaves.
- Nepotism: This is brought up by Thornclaw, who points out that Firestar's third deputy was his daughter's mate, Brambleclaw, who then chose his mate Squirrelflight as deputy when he became leader, and when Squirrelflight becomes acting leader, she chooses her adopted son Lionblaze as the acting deputy.
- Odd Name Out: WarriorClan consists of Monkeystar, Fireface, Bugeater, Bigteeth, Clawwhistle... and Chester. Chester explains that having two names is too much to bother with.
- Old Windbag: Some of the young ThunderClan cats view Graystripe as this, especially when he starts talking about how Firestar would never allow them to behave like that.
- Perspective Flip: The Gathering discussion between Feathertail and Graystripe was originally from Feathertail's POV in A Shadow in RiverClan, and now is from Graystripe's.
- A Pet into the Wild: Several kittypets join WarriorClan.
- Pregnant Badass: When attacking the ThunderClan patrol, the pregnant Gremlin fights just as fiercely as her fellow BloodClan cats.
- Ruler Protagonist: In the "Then" chapters, Graystripe is acting leader of ThunderClan since Firestar is away. He struggles with organizing the cats and making decisions that may save or destroy his Clan.
- Saying Too Much: Snaptooth blurts out to a SkyClan patrol that they’re leaving ThunderClan, and Graystripe's annoyed that he's giving that info away.
- Where It All Began: Graystripe, the only cat that's been around since the first book in the series, decides to travel back to the place the Clans originally lived, where he was born. It's nostalgic and bittersweet for both him and the readers.
