Count the shadows.
Capsule summary below the fold.
3×04 Silence in the Library: Part One of Two. Nudged off course on a research trip, the Doctor, Colin and Sammy arrive a century after the universe’s largest library has been abandoned. They join with a team of 51st century archaeologists to unlock its secrets. What lurks in the shadows? And who is the mysterious woman who seems to know the Doctor’s future?