The bells clang above plague-ridden London as Robin lies helpless, cold, and hungry. The great house is empty, his father is fighting the Scots in the north, his mother is traveling with the Queen, and the servants have fled. He calls for help but only the stones hear his cries. Suddenly someone else is in the house, coming towards Robin. It is Brother Luke, a wandering friar, who takes Robin to St. Mark's Monastery, where he will be cared for until his father sends for him.

At last, a message comes--Robin is to meet his father at Castle Lindsay. The journey is dangerous, and the castle is located near the hostile Welsh border. Perched high in the hills, the castle appears invincible. But it is not. Under the cover of a thick fog the Welsh attack the castle. And Robin is the only one who can save it...