The Deptford Histories, book 2: The Oaken ThroneRobin Jarvis1993

The second book of the Deptford Histories brings readers into a time when a series of dark wars between the bats and the squirrels has raged for years. The squirrel leader, the Starwife, has been betrayed and poisoned. As she lies dying, she summons a falcon to take the magic Silver Acorn to safety. Far away, the squirrel maiden Ysabelle is unaware of the devastating events. But she rescues the Silver Acorn and embarks on a perilous journey to return it. Along the way, she meets Vespertilio, a young bat who has dreamed of waging battle against the squirrels. In this gripping prequel to the Deptford Mice trilogy, the battle of good and evil reaches new heights as Vesper and Ysabelle desperately attempt to save their lands from destruction.