Toxicstar and Shadowstar have had a peaceful alliance together for moons but there is somebody who doesn't want the two clans together. Several StormClan cats end up dead, each death is by the tunnel leading into ToxicClan and each cat is covered in ToxicClan scent. Meanwhile prey is being stolen in ToxicClan, StormClan scent is where the bones are.
Both toms doubt their best friend would purposefully do that to the other's clan but after somebody close to Shadowstar is killed, Shadowstar finally snaps and declares war on ToxicClan.