What book does graystripe die?

Graystripe has never died so far. However, he has been taken in by a Twoleg (human) and lived the life of a kittypet (pet cat). He returned to ThunderClan by the help of Millie, a kittypet and later his new mate. They have kits named Blossomkit, Bumblekit, and Briarkit who later become warriors by the names of Blossomfall, Bumblestripe, and Briarlight respectively.