When her beloved Moonsilver, the unicorn, is nearly killed by a hunter's arrow, Heart sneaks back into her village to get help froth the healer, Ruth Oakes. But even greater danger awaits Heart and Moonsilver in Ash Grove. Rumors of Moonsilver's secret have reached the ears of the cruel Lord Dunraven. Once again Heart must flee, with Ruth's mysterious gift -- a silver thread -- to protect her and Moonsilver.