Gabby Nichols is putting her son to bed when she hears her daughter cry out. ‘Mummy there's a daddy longlegs in my room!' Then the screaming starts. Kevin Alperton is on his way to school when he is attacked by a mosquito. A big one. Then things get dangerous. But it isn't the dead man cocooned inside a huge mass of web that worries the Doctor. It isn't the swarming, mutated insects that make him nervous. With the village cut off from the outside world, and the insects becoming more and more dangerous, the Doctor knows that unless he can decode the strange symbols engraved on an ancient stone circle, and unravel a mystery dating back to the Second World War, no one is safe.