The Mountains of the Moon — Kathleen Duey

Heart has to find a safe haven for her beloved unicorns. With Lord Dunraven looking for them -- and Heart's friends aware that helping her will bring Dunraven's anger -- she has nowhere to turn. If only she knew where her family was -- or who they were. In a mysterious bundle of paper in Dunraven's castle Heart finds a drawing that looks like the design on her baby blanket. The paper is covered with tiny symbols. If she can find out what they mean will they unlock the secrets of the dreams that have been haunting her?