Cluny uses two treacherous foxes, Sela the vixen and her son Chickenhound, to plant a false attack plan in Redwall, while Matthias and his mousemaid friend Cornflower unravel the mysterious motto, "I am that is." It is an anagram for "I Matthias" written years before he was born, another clue for the quest for Martin's sword. Cluny's real underground attack is inventively repulsed by hot porridge and Matthias sees the fearful snake Asmodeus for the first time and realizes that somehow their fates are horribly intertwined.