Cloudtail reports to Bramblestar that the water in the lake tastes weird, and he thinks that it might be poisoned. Bramblestar checks it out and says that it is water from the sun-drown-place, and sees that the water has flooded from there. Later that night the water reaches the camp and ThunderClan has to evacuate.
To the tunnels
When the lake floods and the dens get destroyed, Bramblestar leads ThunderClan into the tunnels and they make their home there temporarily until the water goes down so they can return and repair their home.
The other Clans
Bramblestar goes to see If the other Clans were okay. RiverClan has moved up to higher ground, ShadowClan is having trouble with a gang of aggressive kittypets, but they're too proud to ask for help, and WindClan is settling fine and has gotten a lot of big white birds flying in from the sun-drown-place.
Finding the kittypets
Bramblestar, as well as a few other ThunderClan cats go to the Twolegplace, which has flooded. Due to that, all of the Twolegs have left. The ThunderClan cats try to collect carpets because they have no dry moss. On the way they meet kittypets that have been left behind named Frankie, Jessy, and Minty, and they come to ThunderClan. In the end Frankie is the only one to stay in ThunderClan, and his name later becomes Stormpaw.