It's been ten years since Themis - a giant alien metal robot - was revealed to the world by Dr Rose Franklin. It now stands at the heart of the Earth Defense Corps - in case the makers of Themis return to claim it.
Why did they leave it here?
Rose and her team are still seeking answers to Themis's origins when a second and even bigger robot appears in London's Regent's Park. A military response backfires, reducing half the city to bare earth.
And what if they come back?
As more robots appear across the world, Rose knows it's a race against time to discover where they've come from, what they want and - most importantly - how to stop them...