From a region known only as the Land of Ice and Snow emerges Gulo the Savage, a vicious wolverine in command of a horde of a hundred white vermin (red foxes and ermine) who eat the flesh of their enemies.

Meanwhile, the mercenary Eurasian red squirrel Rakkety Tam MacBurl, along with his companion Wild Doogy Plumm, find themselves at odds with their current rulers, Squirrelking Araltum and Idga Drayqueen, both arrogant, foolish creatures who spend more time on ceremonies in their honor than ruling the kingdom.

When the forces of the Squirrelking are ambushed by Gulo and 30 squirrels are slaughtered, Tam and Doogy are given the chance to escape the trivialities of the kingdom and track the invaders.

The king promises to release them of their bonds after long minutes of persuasion from Idga (they had sworn allegiance to him some seasons before) if they succeed in finding, and returning, the banner.

When two maidens, Sister Armel (the infirmary sister), a squirrel, and the niece to Skipper of Otters, Brookflow (often called Brooky), try to solve the riddle, the spirit of Martin the Warrior appears to Armel, telling her to take his sword and bring it to 'the Borderer who sold and lost his sword', that being Rakkety Tam.

Rakkety Tam takes command of the force and splits them into two groups: one to constantly harass the flesh-eating enemy, and the other to guard Redwall.

Tam and Doogy take the harassment force out to find Gulo's army, encountering the Guosssim, Log-a-Log Togey, and Yoofus.

At Redwall, the other part of Gulo's army attacks the Abbey after slipping past the Long Patrol, led by Shard's mate, Freeta.

The vermin are all killed by armed Redwallers led by Armel and Brooky, but in a fierce battle, Freeta mortally wounds Crumshaw.

Meanwhile, Tam and the rest of his force are buying time for their Guosim allies to clear the Broadstream of a massive fallen tree.