Following complex clues, which promise to lead to Martin's Sword, Matthias climbs high onto the Abbey roof, overlooking the kingdom of the crazy King Bull Sparra.
To finally lift the siege, Constance creates a special crossbow to snipe Cluny dead, only for the warlord to learn of the plan and use it to his advantage.
Cluny captures a travelling spice salesmouse and holds his wife. The fearful husband is forced to enter Redwall and take Cornflower captive in return for his wife.
Cluny seizes the family of a dormouse and threatens to kill them unless their father, Plumpen, betrays Redwall and opens the gates to his huge army of rats.
In the kitchens of Redwall Abbey, Mattimeo and Cornflower fights Vitch, who is a spy for Slagar. Slagar gains entry to Redwall disguised as a leader of a troupe of magicians.
Redwall Abbey awakes to find their young ones are gone, and as they piece the previous night together realize that Mattimeo was right and that Vitch was the slaver's spy.
Mattimeo realizes that the slaves are headed South and will get no help from their parents who are following false trails - they must escape by themselves or not at all.
From Redwall Abbey, Warbeak and her sparra squadrons fly south unaware that their departure is observed by Ironbeak, an evil raven general who will invade Redwall as soon as Warbeak is gone.
Matthias and company ascend the cliffs but come under attack. Across the river Mattimeo leads an escape of his own but is immediately recaptured. Back at Redwall, Ambrose Spike and others set traps for the invading birds.
At Redwall, little Sister May comes up with a potion to drug the birds with food, and at the river it is a frightened Cheek who finally risks swimming, saving Matthias and company by eating vast numbers of nibbling fish.
Slagar reaches The Abyss and forces the slaves across a rope bridge, cutting it away behind him. There is now no way for anyone to pursue him, or so he thought.
Nadaz, henchrat to the king of Malkariss orders the slaves anesthetized. Slagar's rats attack each other and in the chaos are captured by Matthias who demands they help him pursue Slagar.
Redwall Abbey is successfully fighting back utilizing the ruse of Martin's ghost and adds a new friend to its ranks in the form of Stryk, an enormous kite-bird.
Matthias fights the slave master monster but falls into the abyss. Hanging onto a rope, Matthias falls into a basket after it was cut and meets Malkariss himself.