Alex Kingston, Talulah Riley. Ingenious, intriguing, frightening, horrific, epic. Everything about this episode is perfect.
It pulls the viewer in with a great idea at the very start (the 51st century library) and keeps us riveted to the screen with a brisk pace that constantly unveils exciting new details. Some pertaining to the fascinating a-story, some concerning the mysterious b-story and - most daring of all - many of them dropping hints about the future life of The Doctor himself!! Astonishingly good. 10/10
