One summer, Redwall Abbey is surrounded by the army of Cluny the Scourge, an infamously evil one-eyed rat.

Matthias is guided by visions of Martin the Warrior, while the abbey inhabitants prepare the defense of their home against Cluny's impending attack.

Matthias seeks Martin's famous sword, supposedly hidden somewhere within the abbey, helped particularly by Methuselah, an ancient and grizzled mouse who serves as Redwall's historian.

Cluny, meanwhile, attempts to gain entrance to the abbey and murders a defector from his horde, Sela the red fox.

Sela's son, Chickenhound, seeks refuge at Redwall but ends up accidentally killing Methuselah after being caught stealing.

Matthias, his allies now including the Mossflower shrews and the whole Sparra tribe, along with the newly captive Redwall population, battles against Cluny's minions.