Fire and Ice is the second book of the original series.
In the prologue, where the book begins, it shows the fact that WindClan had been driven out of their terriory by ShadowClan, and it goes on to show that WindClan are having some trouble finding a place to live. It then shifts to where the previous book, Into the Wild, ended, with the two newly made warriors, Fireheart and Graystripe, finishing their nighttime vigil. Their first warrior mission, assigned to them by Bluestar, is the task of finding and bringing back WindClan, who were forced out of their original home by Brokenstar, the former ShadowClan leader.
Graystripe and Fireheart journey into WindClan territory and find WindClan far past Highstones, sheltering in a tunnel under a tangle of thunderpaths. They speak with Tallstar, and convince WindClan to come home, as Brokenstar has been driven out and the danger has passed. The WindClan cats return to their territory after a two-day journey, sleeping in Barley's barn for the night, even though WindClan doesn't trust kittypets.
Fireheart and Graystripe are provided with a WindClan escort home, and on their way back to ThunderClan, they decide to take a shortcut by the gorge in RiverClan territory. They are caught by a RiverClan patrol, led by the RiverClan deputy Leopardfur, who forces them into a fight. A ThunderClan patrol arrives to help their fellow Clan mates. Graystripe is engaged in battle with Whiteclaw. Graystripe accidentally shoves Whiteclaw into the river below, who only ends up drowning. Sandpaw almost has the same fate as Whiteclaw, but is saved by Fireheart. The RiverClan cats retreat, promising that Whiteclaw's death will be avenged, but as Leopardfur says--in a different way and at a different time. Fireheart and Graystripe are praised for bringing WindClan home, but their deeds are shadowed by Whiteclaw's death. Later, the two young warriors are given apprentices, Fireheart is given Cinderpaw and Graystripe, Brackenpaw. Fireheart is proud to have an apprentice; he shows Cinderpaw the ThunderClan territory and takes her regularly to training.
One day, when Graystripe, Fireheart, Brackenpaw, and Cinderpaw go out hunting near Sunningrocks, Graystripe falls through the ice into the river and almost drowns. Silverstream, a RiverClan cat and the daughter of Crookedstar, shows up and saves Graystripe's life. As they pad back to camp, Fireheart notices that Graystripe kept glancing over his shoulder--more than once--to gaze at Silverstream. Graystripe comes down with a cold and is confined to the camp, but keeps slipping away, and even Tigerclaw notices his absences. Fireheart is worried about his friend and eventually he follows him out of camp, only to find that Graystripe is meeting with Silverstream near Sunningrocks, having fallen in love with her. Fireheart tells them that their relationship has to stop, and tries to discourage them from seeing each other, but fails, and falls into an argument with Graystripe.
Fireheart trains both Cinderpaw and Brackenpaw while Graystripe is absent, to make sure Brackenpaw doesn't fall behind, and to make sure no cat realizes Graystripe is neglecting his apprentice. Fireheart gets increasingly hostile with Graystripe, who does not want to give up Silverstream, but at the same time, he becomes good friends with Sandpaw.
Leaf-bare arrives and there is an outbreak of whitecough in the camp. One day, Dustpaw returns, saying Tigerclaw wants Bluestar to come and see proof of ShadowClan prey-stealing. However, Bluestar is sick with greencough and she cannot go. Cinderpaw offers to take the message to Tigerclaw, but even though Fireheart disagrees, she slips away. Fireheart follows Cinderpaw's scent trail to the ShadowClan border, only to find her lying beside the Thunderpath, having been hit by a Twoleg monster. He takes her back to camp, but her hind leg is injured too badly, and later it turns out that she will never recover; therefore she can't become a warrior.
Meanwhile, Fireheart meets with his blood sister Princess, and even though the meetings question his loyalty towards Thunderclan, he keeps visiting her. When Princess has a litter of kits, she gives her firstborn to Fireheart to take him to the ThunderClan camp and make him a warrior. The Clan is outraged, but Bluestar decides that they will take in the kit, and names him Cloudkit. Brindleface agrees to feed him. At a Gathering, both ThunderClan and WindClan accuse ShadowClan of stealing prey, having noticed their scent. Later, it turns out that the cats hunting in the Clan territories were Brokenstar and his band of rogue. When all the warriors except Fireheart are out on patrol, Brokenstar and the rogues attack the ThunderClan camp. Fireheart leads the defense and heads straight for Brokenstar, but is attacked by Clawface. Fireheart fights him fiercely, remembering he killed Spottedleaf, but is overpowered and nearly killed. Graystripe then appears and kills Clawface, saving Fireheart. The rogues are eventually driven out, except for Brokenstar, who is blinded by Yellowfang and is taken as a prisoner.
Yellowfang then reveals to Fireheart that she is Brokenstar's mother. Fireheart tells Bluestar about the brave fight the apprentices put up in the battle, and Sandpaw and Dustpaw receive their warrior names, Sandstorm and Dustpelt. Brokenstar loses his leader name and is called by his warrior name, Brokentail. A fight with WindClan against RiverClan and ShadowClan tests Fireheart's and Graystripe's loyalty to their Clan. Graystripe attacks only the ShadowClan warriors, and it is very clear that his loyalties have been divided. Silverstream attacks Fireheart, not realizing that he is Graystripe's best friend. Fireheart turns on her, and despite her being Graystripe's forbidden love, pins her to the ground. As the book describes, Fireheart can feel Graystripe's shocked eyes locked on him, and Fireheart releases Silverstream without so much as scratching her. Darkstripe sees Fireheart mercifully release Silverstream, and tells Tigerclaw about it. At one point in the battle, Fireheart gets nearly killed by Leopardfur, but Tigerclaw watches on without helping him. Fireheart is certain now that Tigerclaw can never be trusted. After the battle, Tigerclaw confronts Fireheart, questioning him about his loyalty to ThunderClan, but the friendship between Fireheart and Graystripe seems to be back to normal again.
Leader: Bluestar-blue-gray she-cat, tinged with silver around her muzzle
Deputy: Tigerclaw-big dark brown tabby tom with unusually long front claws
Medicine Cat: Yellowfang-old dark gray she-cat with a broad, flattened face, formerly of Shadowclan
Warriors: Whitestorm-big white tom Apprentice, Sandpaw
Darkstripe-sleek black-and-gray tabby tom Apprentice, Dustpaw
Longtail-pale tabby tom with dark black stripe Apprentice, Swiftpaw
Runningwind-swift tabby tom
Willowpelt-very pale gray she-cat with unusual blue eyes
Mousefur-small dusky brown she-cat
Fireheart-handsome ginger tom Apprentice, Cinderpaw
Graystripe-long-haired solid gray tom Apprentice, Brackenpaw
Apprentices: Sandpaw-pale ginger she-cat
Dustpaw-dark brown tabby tom
Cinderpaw-dark gray she-cat
Brackenpaw-golden brown tabby tom
Queens: Frostfur-beautiful white coat and blue eyes
Goldenflower-pale ginger coat
Speckletail-pale tabby, and the oldest nursery queen
Elders: Halftail-big dark brown tabby tom with part of his tail missing
Smallear-gray tom with very small ears; the oldest tom in ThunderClan
Patchpelt-small black-and-white tom
One-eye-pale gray she-cat, the oldest she-cat in ThunderClan; virtually blind and deaf
Dappletail-once-pretty tortoiseshell she-cat with a lovely dappled coat
Leader: Nightpelt-old black tom
Deputy: Cinderfur-thin gray tom
Medicine Cat: Runningnose-small gray-and-white tom
Warriors: Stumpytail-brown tabby tom Apprentice, Brownpaw
Wetfoot-gray tabby tom Apprentice, Oakpaw
Littlecloud-very small tabby tom
Queens: Dawncloud-small tabby
Tallpoppy-long-legged light brown tabby she-cat
Elders: Ashfur-thin gray tom
Leader: Tallstar-a black-and-white tom with a very long tail
Deputy: Deadfoot-a black tom with a twisted paw
Medicine Cat: Barkface-a short-tailed brown tom
Warriors: Mudclaw-a mottled dark brown tom Apprentice, Webpaw
Tornear-a tabby tom Apprentice, Runningpaw
Onewhisker-a young brown tabby tom Apprentice, Whitepaw
Queens: Ashfoot-a gray queen
Morningflower-a tortoiseshell queen
Leader: Crookedstar-a huge light-colored tabby with a twisted jaw
Deputy: Leopardfur-unusually spotted golden tabby she-cat
Medicine Cat: Mudfur-long-haired light brown tom
Warriors: Blackclaw-smoky black tom Apprentice, Heavypaw
Stonefur-a gray tom with battle-scarred ears Apprentice, Shadepaw
Loudbelly-a dark brown tom Apprentice, Silverpaw
Silverstream-a pretty slender silver tabby
Whiteclaw-a dark warrior