The Doctor and Amy discover a sub-aquatic base that's been attacked by a sea monster from another world, but its crew are living in fear of something else - a voracious horror that hides in their shadows. The Vashta Nerada.
This is your chance to be the Doctor.
Are you ready for the challenge?
The Vashta Nerada are ravenous hunters able to strip the meat from a body with a frightening speed and efficiency. They tend to avoid light, often concealed in patches of dark that resemble shadows, hence the general warning to 'Stay out of the shadows' if you suspect these creatures are close.
Even species that are not consciously aware of the threat posed by the Vashta Nerada seem to sense their menace. As the Doctor once observed, 'Almost every species in the universe has an irrational fear of the dark. But they're wrong. Because it's not irrational. It's Vashta Nerada.'
In their natural state the Vashta Nerada are tiny but when they gather in large numbers they're able to animate objects, including the remains of humans. Their adaptability is possibly one reason for their universality; they have encountered the Doctor in different centuries and their race has blighted numerous planets across the cosmos.