Thunder must figure out how to help his father Clear Sky and uncle Gray Wing, leaders of two cat once close groups that are gradually drifting apart, solve the boundary threats Clear Sky creates due to his insecurities as leader. Clear Sky uneasily leads the forest cats, feeling it is his role but finding it difficult to hide the insecurities he feels. He feels especially a great need to protect and provide for his cats, and to prove his own competence as a leader. Many moor cats, and even some forest cats, mention how he has changed for the worse. Gray Wing is still respected in his group of moor cats as leader, but weakened by asthma since a forest fire in a previous book, he often defers judgement to another reliable cat in their clan. Thunder is caught in the middle. Raised by the moor cats but most recently living with the forest cats, Thunder cannot tolerate his father's recent banishment of Frost, an injured white cat. Thunder and Frost go to live with the moor cats.
As distrust grows between the groups, both begin preparing for battle, and the kits begin learning as well, though some cats question whether they are old enough. Both forest and moor cats also welcome new additions. Several rogue (loner) cats join the forest cats, and two expectant mates (Gores Fur and Wind Runner) are formally welcomed into the moor cats' group. Wind Runner gives birth to four kits shortly after, though she loses one.
The moor cats' hollow is also home to three slightly older kits, to whom Gray Wing is stepfather. They belong to his mate, Turtle Tail. Their father Tom, a housepet and bully, comes searching for them and absconds with them. Turtle Tail, Thunder, and one more from their group follow them into human territory to (with difficulty and some help from a kind rogue cat) retrieve them. Turtle Tail is hit by a car, a tragic event that is in one way at least turned to their advantage: by pointing out that Tom will be forever remembered as the killer of his children's mother (since he took the kits against her will), Thunder and his companions dissuade him from following them back to camp.
Gray Wing is able to establish a meeting with Clear Sky, but Clear Sky turns it into a trap. Gray Wing is lucky enough not to trust him entirely and to bring enough backup to hold out until Thunder can go ask for help from the other moor cats. A battle – the first battle – ensues, with several cats dead and no winner when it ends. Clear Sky ends the battle when he cannot bring himself to kill his brother, and orders his cats back to camp before him because he judges himself weak. The cats remaining in the meeting place are all quite cognizant of the meaninglessness of the day's deaths. A number of spirit cats, including Turtle Tail and Wind Runner's lost kit (Emberkit), appear and discuss this with them. Clear Sky begins to recognize his faults, and the book ends with some hope for the two groups to establish peace and even cooperation.
Best part of story, including ending:
It was helpful to have various characters' positive and negative characteristics clearly portrayed without all these characters being portrayed as 100% good or bad. For instance, Thunder must struggle between his love for his father and his distaste for what his father has become. Gray Wing still remembers the good cat Clear Sky was. And Clear Sky, as the story moves on, clearly is dealing with certain insecurities.
Best scene in story:
When Emberkit (the lost kit) is buried, Turtle Tail is simultaneously remembered. Even though they cannot bury her, since her body could not be brought back from human territory, her importance is still recognized. Later, when she returns as a spirit, she also backs up their actions and says she appreciates them.
Opinion about the main character:
Thunder is divided between his father and uncle, but is able to face his internal struggle to figure out how to balance it, even though it can't all be resolved the way he wants it to be.