In The Darkest Hour.
yes, but Bluestar did die in a dangerous path, leaving him with Clan athority
Though Bluestar appointed Firestar as ThunderClan's leader right before she died in A Dangerous Path, he did not become ThunderClan's official leader until The Darkest Hour. ❄ Blizzardpelt ❄Freezing in the Summer! 17:56, December 16, 2012 (UTC)
He had the title leader when Bluestar died in A Dangerous Path, but received his nine lives in The Darkest Hour. -Feathermist