In 2073 the majority of the world's population was wiped out. 25 years later people are only really beginning to work out what happened.

Ryssa is a doctor at the Sanctuary, a military base in the heart of London. Along with Captain Sam Matthews and his team, she is given the chance to explore the farthest reaches of the city.

As they learn more about the things lurking in London, they begin to make some startling discoveries about the world they live in. Discoveries that could change the way in which they look at the place they call home.