The book begins where the last one ended: Graystripe is filled with horror as he and Millie stand on the ruins of the Clan territories. Graystripe surveys the damage to the ThunderClan camp, noting that only the medicine den has not been destroyed. He curls up in it, and Millie comes to lie beside him. He tells her about medicine cats and their duties. Then, Millie decides that it is time to go and find out where the Clans went.
After exploring the destroyed territories, Graystripe and Millie find Ravenpaw's farm. There, they meet Ravenpaw and Barley, who are all too happy to tell them where the Clans went. Graystripe and Millie thank them, and stay for a little while in their barn. The next morning, Ravenpaw and Barley show the adventurers the path they must follow, and they make their goodbyes. After Graystripe and Millie are long gone, Ravenpaw has a moment of quiet contemplation. When Barley asks him what's wrong, Ravenpaw nostalgically explains that Graystripe was his last connection to the forest.
Graystripe and Millie spend a long day traveling, and they have a variety of misadventures. These include being attacked by a homeless man near a rising highway, and having an argument over whether to get some cat food from a Twoleg nest. That night, Graystripe dreams of Firestar leading the Clans to their new home.
The next day, Graystripe and Millie accidentally cause a stampede of sheep. After escaping, the duo wind up at a truckstop, and Millie decides to get some kittypet food. She is given some without trouble, but Graystripe is hit by a broom-wielding lady when he tries to get some. This causes a dispute, and Graystripe storms off. He neglects the ancient adage, "Look both ways when you cross the street", and is thus hit by a car.
Graystripe wakes up and sees Millie, along with another cat. The newcomer introduces himself as "Diesel", and Millie explains that Diesel has been helping out. Graystripe has injured his back, so he has to stay at the truckstop until he can recover. During his stay, he begins to worry that Millie is falling in love with Diesel. Graystripe and Millie explain their plans to Diesel, and he tells them that there are often trucks traveling to the sun-drown place. He explains that Graystripe and Millie could ride one to the Sun Drown Place, then keep going until they reached the Clans. After this, Graystripe and Millie reaffirm their feelings under the stars.
The next day, Diesel identifies a good truck. Graystripe and Millie board it after bidding Diesel farewell. The truck drives for a while, and eventually stops at a place called Hare Hill Inn. The duo decide to rest outside until the Twolegs come back. However, they are attacked by kittypets who try to claim ownership of the land outside Hare Hill Inn. The adventuring duo win the fight, but the truck starts to leave without them. They chase it and try to jump on. Millie lands safely, and saves Graystripe before he falls off the truck.
The next stop for the truck is the sun-drown place. Graystripe spies a forest nearby, and the duo goes to investigate. The walk all day, and eventually reach the forest. Graystripe asks a jumpy cat if he has seen anything resembling the Clans, and gets a yes in response. Noticing the full moon, Graystripe tells Millie that there is a Gathering going on. Before they descend to the lake, Graystripe and Millie admit their love for each other, and become mates.
The newly mated couple crosses the bridge to the Gathering island in awe. The reach the clearing, where Firestar, Leopardstar, Blackstar, and WindClan's leadernote are sharing news. Firestar is shocked to see Graystripe, and happily rushes down to greet his best friend. As the Clan cats rejoice, Graystripe gestures to Millie and says that he has someone he'd like them to meet.
Tropes that appear in this volume:
- Abandoned Area: The Clans' territories and camps. Graystripe and Millie wander through them as they look for the Clans, (since they weren't aware that the Clans have left.)
- Alertness Blink: Graystripe and Millie get an exclamation point above their heads when a homeless Twoleg tries to grab them.
- Colorization: Graystripe's Adventure was originally drawn and released in black-and-white, in three different volumes. James Barry later colorized it and it was re-released as a single volume.
- A Day in the Limelight: This manga trilogy serves as Graystripe's.
- Desolation Shot: Much of the start of the start of the volume involves shots of the completely destroyed forest and ThunderClan camp.
- Downer Beginning: The book begins with Greystripe finally arriving at ThunderClan. ...or what's left of it, as he and Millie sadly discover that the Twolegs have completely decimated the forest.
- Earn Your Happy Ending: After three books of being separated from ThunderClan, Greystripe and Millie not only reach the Clans, but become mates as well.
- Eye Cam: This effect is used in the scene after Graystripe is hit by a car, to show his point of view as he passes out and then awakens afterward.
- Gilligan Cut: Graystripe says at the bottom of a page, "But I won't be sleeping tonight." Next line on the following page: "It's the cold that wakes me."
- Look Both Ways: Graystripe gets hit by a car when he isn't paying attention to where he's going. Fortunately he survives, but his shoulder is injured.
- Only Six Faces: In the earlier graphic novels by James Barry, there are hardly any variations in character design. This isn't a problem usually, because in the Graystripe's Adventure series not very many characters appeared at the same time, but in crowd shots it's very problematic. It's especially hilarious in the gathering at the end when there are four cats in the crowd who look exactly like Ravenpaw (fortunately, this was improved in the full-color rerelease.)
- Series Continuity Error:
- At the end, when Graystripe and Millie come to the Gathering, the tree-bridge is shown as having its roots on the mainland. In Starlight, it originally fell from the island to the mainland, so they should be approaching its top, not its roots.
- In the original black-and-white manga, Tallstar is the leader of WindClan at the Gathering, but in the actual books, he died before they started using the island for Gatherings. He is replaced with Onestar in the full-color rerelease.
- Too Desperate to Be Picky: Clan cats prefer freshly-killed prey and find pet food disgusting and degrading to eat. For this reason, Graystripe insists that he and Millie must not eat any pet food and should instead hunt for themselves while on their way to find the Clan. Finally, too hungry and tired to keep arguing with her, he agrees to eat some, only to be chased out of the building by a woman wielding a mop.
- Unexpectedly Abandoned: Graystripe finally escapes from the humans and finds ThunderClan's territory and camp again, but is shocked to find that all the Clans seem to be gone, as they left for new territory without him.
- Watching Troy Burn: Graystripe triumphantly returns to the forest, only to find it completely destroyed. He wanders around the destruction for a little while before Millie convinces him that his Clanmates are still out there somewhere.
- You Can't Go Home Again: After Graystripe is captured by Twolegs, it takes him several moons to escape and find his way back to the forest... but that's when he realizes there is no forest - it's been destroyed by Twolegs.
