Dark River

Fallen Leaves' Story
In Dark River's prologue, it is revealed that there are hidden caves beneath the moorland. Fallen Leaves, a mysterious cat not seen before in any of the books, enters this cave, meeting a misshapen, old cat by the name of Rock, who explains to him that to be a sharpclaw (an equivalent to the Clans' warriors), he must find a way out of the tunnels and onto the moor. Unfortunately, when Rock asked if it would rain, Fallen Leaves said no, because he was afraid that Rock would make him wait until another day if he said yes. Fallen Leaves enters the tunnels and is trapped in the tunnels then when it does rain he is trapped and drowns and never comes back out ever again. He later helps Jaypaw get out in the end of the book.
[edit]Jaypaw's Story
Also ThunderClan medicine cat apprentice Jaypaw finds a washed-up stick when he is out gathering herbs with his mentor, Leafpool. It has odd scratches on it; some that are crossed out and some that aren't. He doesn't know why, but the stick feels very important to him, to the point that he half drowns himself to save it from the depths of the lake. As he struggles to figure out what it means, he has a dream in which he experiences what Fallen Leaves experienced. Jaypaw then understands what the scratches mean and that the last uncrossed one was Fallen Leaves' mark. Cinderpaw then falls from the Sky Oak, breaking her back leg. He soon discovers that his mentor, Leafpool, is determined to save the apprentice's leg. As the medicine cat's determination begins to border on an obsession, he begins to wonder why. One night, he falls asleep and he wakes up in a strange forest. There he meets Cinderpaw, unhurt, who leads him to a camp filled with familiar smells; ThunderClan's previous home in the forest. Cinderpaw describes how she once lived there before the Great Journey and asks Jaypaw to tell Leafpool that she is proud of her, and that she has learned far more than she could have ever taught her. By then Jaypaw is officially confused, but when looking into Cinderpaw's eyes, he sees a series of flashbacks from her previous life. Jaypaw realizes that when Cinderpelt, the former ThunderClan medicine cat, died in Twilight she was reincarnated as Cinderpaw, without Cinderpaw herself knowing it. Jaypaw tells Leafpool what he has discovered and his mentor agrees with him. However, when Cinderpaw wakes she doesn't remember the dream (only that Jaypaw had been able to see in it).
[edit]Lionpaw's Story
Lionpaw becomes best friends with Heatherpaw, a beautiful WindClan apprentice, and begins meeting her at night. Hollypaw discovers their secret and Lionpaw begins to be wary of his "nosy" sister. Afterwards, Heatherpaw and Lionpaw begin meeting in hidden tunnels that no Clan cat has ever seen before (the same tunnels that Fallen Leaves drowned in). They name their play Clan DarkClan, of which 'Heatherstar' is leader and 'Lionclaw' is deputy. They meet together every night they can. Tigerstar, who meets Lionpaw in ghostly apparitions, like he did to Hawkfrost and Brambleclaw, starts teaching him additional battle moves that even his mentor, Ashfur, doesn't know, though Brambleclaw seems to recognize them. When Lionpaw starts to teach the moves to Heatherpaw, Hawkfrost scolds him for showing battle moves to the enemy, and under pressure, Lionpaw must choose between his love of Heatherpaw, and loyalty to the warrior code and ThunderClan. He chooses to remain loyal to his Clan and leaves Heatherpaw, who is extremely hurt and betrayed, though she understands his decision in the end.
[edit]Hollypaw's Story
During a Gathering, RiverClan reveals that their Clan is facing a "small problem" and that they are being forced to live on the island for a short while. Though Leopardstar is fiercely protective of her Clan and refuses to elaborate, Hollypaw knows something is not right, because her friend Willowpaw and the rest of RiverClan are acting extremely nervous. She informs Firestar about her concerns. However, he does not believe this is ThunderClan's problem and refuses to take action. He and the rest of the Clan continue preparing for a battle against WindClan even though it is not certain that a battle will ever occur. Hollypaw heads out to RiverClan on her own. When she arrives, Willowpaw shows her how Twoleg kits (children) are attacking their camp. Hollypaw is kept with RiverClan so she cannot tell anyone about their secret because they think she is a spy. However, her brother Jaypaw has a dream that reveals her location, and Squirrelflight comes to retrieve her.
[edit]Conclusion
Near the end of the book, all three stories combine: Jaypaw and Leafpool must go to WindClan to take Onestar a message from Firestar about not shedding unnecessary blood in a battle over something that may never happen, while Hollypaw convinces Mousefur and Firestar to do something. When they arrive, Gorsetail's (a WindClan queen) kits (Sedgekit, Thistlekit and Swallowkit) are missing and WindClan blames RiverClan, saying that there will be a battle if RiverClan does not return the kits. Jaypaw and Leafpool return to camp and Lionpaw tells his brother and sister about the tunnels, where he thinks the kits may have gone. They enter the caves, meeting up with the WindClan apprentices Breezepaw and Heatherpaw, who share their motive for being there. Jaypaw is guided by the spirit of Fallen Leaves and the group find the kits behind a boulder that blocked the tunnel. It starts raining and the tunnel floods, but Jaypaw figures a way out just in time and they return the kits, saving the Clans from an unnecessary battle. The tunnel is blocked during the flood, and Lionpaw states that it ended the most important friendship he ever had