Doctor Who 9x6 - The Woman Who Lived (2)

England, 1651. A deadly highwayman known only as 'TheNightmare' plagues the dark streets of London, hisfire-breathing accomplice by his side. There's somethingclearly more than human here, and that includes the loot asmuch as the outlaws. Who are these creatures, and are theyenemies to be fought, or friends who might possibly save theDoctor from certain doom on the gallows?.