The forest is a dangerous place for any animal, especially one as small as a mouse. In the past, the mouse world endured a tyrannical Weasel Warlord until a noble band of mouse soldiers fought back. Ever since, the Mouse Guard has defended the paces and prosperity of its kingdom. For generations, this league of scouts, weather-watchers, trailblazers, and protectors has passed won its knowledge and skills.

Now three of the Guard's finest have been dispatched. The mission seems simple: They are to find a missing mouse, a grain merchant who never arrived at his destination. But when they find him, they make a shocking discovery—one that involves a treacherous betrayal, a stolen secret, and a rising power that has only one goal: to bring down the Guard...