Code of the Clans

In the introduction, it summarizes how the Clans (including SkyClan) was formed. It then cuts to Leafpool introducing the warrior code to us (as we are rogues visiting Leafpool to learn more of the code.) Each Code starts with Leafpool giving a hint about the story and how the code was formed. Sometimes there is an extra story after it.
Code One tells the story of Cloudberry of RiverClan and Ryewhisker of WindClan. Cloudberry is expecting Ryewhisker's kits and Ryewhisker believes the kits will end the territorial dispute between the two clans. But instead, in a battle, Ryewhisker was killed when he was trying to defend Cloudberry from his Clanmates. This led the Clans to form the first code and start a gathering place.
Code Two begins at the gathering when Brindlestar, leader of ShadowClan, complains to ThunderClan. ThunderClan accuses ShadowClan of stealing prey and a fight starts to break out. The fight was interrupted when a branch falls between the two Clans and no cats were hurt. It was a sign from StarClan that no Clan cat may cross the border and forms the next code. (In a mini-story, One-eye, known as White-eye and Dappletail wish to catch a fish to know why RiverClan like the prey so much.)
Code Three tells the story of Splashheart of RiverClan and another battle with ThunderClan over the Sunningrocks. Splashheart is guided by a StarClan cat and RiverClan wins over the Sunningrocks and celebrate by feeding the elders and kits, and hints that Splashheart will become leader of RiverClan one day. (In a mini-story, Longtail and Darkstripe are going out hunting for the elders, but Darkstripe eats the fresh-kill intended for Poppydawn and Longtail could do nothing. Since they could not make it on time, Poppydawn dies from greencough and Longtail regrets deeply.)
Code Four starts at ShadowClan territory when Driftkit and Fallowkit play with fresh-kill and were scolded by their leader, deputy and mother. An owl soon swoops in the camp and takes the fresh-kill away and Lilystar says its a sign from StarClan.
Code Five begins with a worried WindClan queen named Daisytail, who worries that her son is too young to be in a battle against ShadowClan. She and a queen from ShadowClan stop the battle and tell their leaders that their apprentices should still be kits until they are at least six moons old. (In a mini-story, during the reign of Brokenstar and battle to drive out WindClan, Flintfang watches as his apprentice [who is three moons old] dies.)
Code Six starts with the RiverClan's medicine cat, Meadowpelt, as he overhears some of the new warriors are going to jump the gorge on the full-moon. Meadowpelt goes to StarClan for answers and finds out the warriors must stand vigil during the next to think about being a warrior and the warriors save the nursery from a fox and learn the true importance of being a warrior. (Squirrelflight tells us what do at a vigil in a mini-story.)
Code Seven tells the tale of Acorntail, as he is chosen deputy for WindClan. But he keeps messing up and tells Featherstar that she must choose a different deputy. Featherstar notices that Acorntail didn't learn how to lead and gain loyalty which is taught through an apprentice and Acorntail decides he must have an apprentice.
Code Eight starts when Beechstar, leader of SkyClan, gives his leadership to his son Mothpelt. Mothpelt wishes to avenge his father's death and leads an attack to RiverClan. The river was over flown and Robinwing and Maplewhisker, the deputy, has to save the warriors from drowning. Mothpelt gives up his position to Maplewhisker and forms a new code. (In a mini-story, Tallstar talks to Bluestar about his last choice in making Onewhisker as deputy.)
Code Nine begins when the Shadowclan deputy dies from greencough soon after their leader died. In order to decide a new leader, Jumpfoot and Mossfire fight to the death for the position. Redscar, the Clan's medicine cat, turns to StarClan for the answer. They tell him they must chose a new leader and the leader must chose a new deputy immediately. Redscar chooses Flowerstem because she watched her sister, Mossfire, die right in front of her and Flowerstem's only thoughts were to help the clan.
Code Ten starts at a gathering and all four Clans were attacked by ShadowClan, led by Ripplestar. As Ripplestar attacks Finchstar, leader of ThunderClan, StarClan sends clouds over the moon and kills Ripplestar with a bolt of lightning - giving a sign to all Clans.
Code Eleven begins when a SkyClan warrior named Poppycloud and her apprentice accidentally overstep the ThunderClan border and were caught. The leader of ThunderClan goes to the SkyClan leader and tells him what is going on. Poppycloud explains that they could not smell the border because it was not freshly made, which brings up the decision to remark their borders daily. (In a mini-story, Whitestorm teaches Firepaw, Graypaw, Ravenpaw, Sandpaw, and Dustpaw about border tactics.)
Code Twelve begins when the RiverClan medicine cat, Graywing, and a couple of warriors see WindClan kits fall into the gorge. Graywing says that it is only WindClan's loss and there is nothing they can do. But the StarClan kits come to Graywing and tell her the importance of kits in a Clan and Graywing and the warriors get the kits' bodies out of the gorge. (In a mini-story, Tigerkit (Tigerstar as a kit) is saved by a couple of warriors from ShadowClan from a fox.)
Code Thirteen starts at the gathering, where Darkstar, leader of SkyClan, gives a huge piece of territory to ThunderClan. Raincloud out loud tells him that he is wrong to do that, and Darkstar makes a new code so a leader won't be out staged by their warriors like that. (In a mini-story, Cloudstar talks about a broken promise.)
Code Fourteen starts with the ShadowClan medicine cat, Mossheart, seeing her Clanmates die in a battle skirmish. She and the other Clan medicine cats go to Moonstone together and are both told that this unnecessary death must stop. It also initiates a place where all medicine cats are defined from clan skirmishes and a place where they all share tongues with StarClan.
Code Fifteen starts with Lionpaw stalking Pinestar to the twoleg border. Pinestar tells Lionpaw that what he saw is absolutely secret and must not tell other cats. Soon Lionpaw finds out that Pinestar wishes to live with twolegs and Lionpaw pushes him to tell the Clan this. Pinestar thanks him and tells him that his future name will be Lionheart. (In a mini-story, Sandstorm tells about her thoughts on Fireheart.)
In the end, Leafpool tells what was not included in the warrior code and says goodbye.
The cover shows (from left to right) Blackstar, Firestar, Tallstar, and Leopardstar. Below them, they are surrounded by a group of cats, so the picture presumably depicts a Gathering.