Mossflower, the second book in the Redwall series, tells the story of the founding of Redwall Abbey and of Martin the Warrior's part in it. The peaceful woodland creatures of Mossflower woods are invaded and conquered by a wild cat and his army of weasel, stoats and ferrets. After mounting an unsuccessful attempt at rebellion, the woodlanders slowly retreat further and further into the woods and out of the grasp of the cat. He dies leaving his evil daughter, Tsarmina to rule. Evil as she is, no matter what plan she hatches, she can't seem to subdue the woodlanders and enslave them as she desires. The woodlanders have pinned their hopes on the return of the onetime ruler of Mossflower, the great badger, Boar the Fighter. He had long since left the woods on a quest to the volcano, Salamandastron, and never returned. His daughter, Bella, feels sure that he is alive and must return to vanquish the evil Tsarmina.

Martin the Warrior, a bard-like mouse named Gonff and Dinny the mole leave to find and bring back Boar the fighter. They encounter many adventures along the way, meeting friends and foes, leaving the woodlanders to fend off the increasingly maddened Tsarmina. They do find Boar but his destiny lies in the defeat of an evil sea rat, not in his return to Mossflower. He forges a sword for Martin, however, from the fires of Salamandastron (which is really not a volcano but a huge forge in the mountain) and charges Martin with the duty of the defeat of Tsarmina in his place.

Martin and his friends return to Mossflower just as a plan to flood the evil cat's castle is underway. With Martin's battle plan, the cat's castle is destroyed and the army subdued. Martin himself battles the cat and defeats her. In the end, the mice plan to build an abbey there in the woods dedicated to peace and designed for the protection of the woodlanders. Martin becomes a legend and his saga told to all successive ages of Mossflower inhabitants.

There are many similarities to the original Redwall story, such as a thoroughly evil antagonist, the hero away on a quest during most of the story, the quest ending in finding a sword and a battle between so-called peaceful creatures and trained armies. In this story, however, the hero Martin is portrayed as a noble warrior from the beginning. He has great courage and chivalry and is proven time after time. Another pleasant part of this story is the bard mouse Gonff. He is a delightful character, making up songs and poetry at every turn in the story. The woodlanders are quite ingenious in their resistance to the wild cats (squirrel archers, otter commanders and tunneling moles). I kept thinking that they were doing pretty well without Boar the Fighter. I still found the dialogue trite at times and the plot pretty obvious. When Tsarmina starts to have nightmares about water, we know she's going to die in water.

Mossflower was a good prequel to Redwall in that references made in the first book were explained and the stage set for other stories. Other books in the series suggested by this story include the titles Salamandastron, Martin the Warrior, Luke (father of Martin), Mattimeo (son of Matthias) and more. They all have similar themes in the defeat of evil rats or other vermin by the peaceful, good woodlanders.