The key that unlocks Lucy's world has a dangerous power.
It's Easter Saturday, and Joe Hopkins is out riding with his brother. When his horse throws him off, he lands, quite literally, in Tudor England.
Joe has learned about the Tudors at school. But if he thinks that will help him, he soon discovers that he knows both too little and too much.
He doesn't realise that by giving Lucy his St. Christopher, he is putting her in danger. And when it is taken from her, he faces an even greater peril to get it back.