In the countryside of France in 1165, the old duke has died, and a child has assumed his place. The peasants find themselves unprotected and at the mercy of the evil Sauval, a "treacherous, bloodthirsty pair of brothers" who take their money and possessions and kill anyone who gets in their way.

Fifteen year old Conan is training for the knighthood and witnesses the Sauval firsthand as they plunder a neighboring castle. He rescues the only survivor of the family, their daughter Anne. She is taken in by the family that Conan is staying with.

By the time he is 20, Conan's father and brother have been killed by the Sauval. Anne tries to convince him that the Sauval will continue to strike his family, thus improving their position in the area, but Conan doesn't believe her until another brother is killed. Finally, determined to return the Red Keep to its rightful owner, Conan vows to avenge his losses and to stop the Sauval brothers from taking permanent control of the countryside.

His journey takes him to Vezeley to gather information from the Lord Abbot who secretly supports the Sauval. Here, Conan sacrifices his dignity by cutting his long hair, a sign of his rank in society, and learning the ways of the masons. He works alongside the masons as they do repair work for the abbot and is able to eavesdrop on the abbot and his men. The abbot then asks Conan and the masons to rebuild the Red Keep for the Sauval brothers. Conan convinces the masons to do the work, not for the abbot, but so that Anne can claim the Red Keep for herself. The plans and resulting battle make for a fast-paced, suspense-filled story.

The Red Keep is great reading for boys and girls. It's full of plenty of action and there is a subtle romantic storyline wound through. Allen French has created a believable main character that shows human weakness, yet is cunning and thoughtful at the same time. He has Conan realistically growing from a proud, rash youth into a loyal, kind man. All this occurs in 12th century France, which gives the reader a detailed picture of medieval life and the feudal system.

I agree with Bethlehem Book's recommendation of a reading age of 10 and up since the book contains some fairly violent scenes.