Arriving on the planet Cashel, the Tenth Doctor witnesses a strange masked ball. To guarantee peace, Prince Zircon has to choose a bride from the Bog People - dead men and women who have been resurrected as slaves. Or as warriors. But Zircon is in love with the enslaved Princess Ash, whose parents were deposed and executed by the current Queen. As usual, the Doctor has walked right into trouble, and it's up to him to sort it out.