Fleeting Shadows is about a rabies outbreak in ShadowClan. The main character, Falconpaw, lives in ThunderClan, and is one of the first cats to notice ShadowClan's odd behavior at Gatherings and on border patrols. The infected cats experience high fevers, muscle spasms, dizziness, fatigue, hallucination, aggression and irritability, foaming at the mouth, and eventually, death.
   Once the ShadowClan leader is infected, ShadowClan announces what is going on at the Gathering. One of their warriors was bitten by a rabid fox while hunting, and they spread the deadly disease to the rest of the cats. All of the Clans are terrified that their cats will be the next to be infected, and it's up to Falconpaw to find an herb that can save them all.