There are currently seven sub-series, each containing six books except for the seventh sub-series, which is currently in progress. The first, "Warriors" (later re-titled "Warriors: The Prophecies Begin"), was published from 2003 to 2004, and details the adventures of a “kittypet” (housecat) named Rusty who joins ThunderClan, one of the warrior cat clans who live in the forest, and must leave his Kittypet life behind to learn “the warrior code” and how to be a good leader who can save the clans from destroying themselves. "Warriors: The New Prophecy" (2005-2006) continues with a focus on the next generation of young cats, and chronicles the four Clans' journey to a new home.