The Forgotten Warrior is the first book of the The Omen of the Stars arc. The author is Cherith Baldry, and it was published on November 22nd, 2011. The book is written from the point of view of 5 cats; Jayfeather, Ivypool, Dovewing, Lionblaze, and Hollyleaf.
As a full-scale battle with the Dark Forest looms near, tensions between the warrior clans are high, while spies within the clans work for the Dark Forest.
Ivypool, a young warrior of ThunderClan, is one of these spies, and is training in the Dark Forest, with clan cats and even other clan-mates, and her role of the spy continues to become dangerous every day.
Soon, Sol returns, and does not deny that he had saved Poppyfrost's kits. He is welcomed, but not trusted by the Senior warriors.
Dovewing, Ivypool's sister, is haunted by dreams of the mountains. Dovewing and Ivypool are sent to find Sol, to find out if he betrayed them to WindClan. During their serach, they are nearly found out by a WindClan patrol, until they meet Hollyleaf.
Hollyleaf introduces herself, and tells ThunderClan the truth of Ashfurs death, and also who actually saved the kits, and prepares the ThunderClan cats for battle.
Jayfeather he is told by Yellowfang to tell Cinderheart, the reincarnation of Cinderpelt, who she was in her past life. However, Leafpool tells him that Spottedleaf says they should keep quiet about it.
Lionblaze is disappointed that Cinderheart believes they cannot be mates because of the prophesy, and explains this to Jayfeather after remembering her past life, and feels she should be Medicine cat again.
With the Dark Forest battle on the horizon, will the clans work together? Or fall into distrust?