Fablehouse, a mysterious mansion surrounded by ancient woodland, is Heather's new home. Roaming the countryside with some of the other mixed-race kids who are in care there, she finds a stone tower that feels strangely magical. There they meet Palamedes, the Black knight from King Arthur's court. He warns them that danger lurks in a world beneath their feet.

Heather, Pal and friends set off to rescue children who have been taken to this threatening underworld. No child will be forgotten on their watch. Heather and friends realise they have been specially chosen for this quest. They must use the talents they've been given in the battle to save Fablehouse and all the children who have found shelter there.