The Doctor's second heart was taken from his body -- for his own good, he was told. Removed by his sometime ally, sometime rival, the mysterious time-traveller Sabbath. Now, as a new danger menaces reality, the Doctor finds himself working with Sabbath again. From a seance in Victorian London to a wild pursuit on Dartmoor, the Doctor and his companions work frantically to unravel the mystery of this latest threat to Time... Before Time itself unravels.