Erlenburg, winter 1390: kitchen boy Hannes comes across a stranger in the snow-bound castle moat – half-frozen, but still alive! He takes him to the safety of the larder next to the castle’s kitchen. It’s not long before Hannes and his friends start wondering who this elegantly clad, mysterious nobleman might be. When the barely recovered stranger suddenly disappears, only to turn up in the castle dungeon soon after, the children realise it’s high time to get to the bottom of his secret. And once again, readers are called on to help the young detectives solve the puzzle!