When they first arrived, they came quietly and stealthily as if they tip-toed into the world when we were all looking the other way. Ade loves living at the top of a tower block. From his window, he feels like he can see the whole world stretching out beneath him. His mum doesn't really like looking outside - but it's going outside that she hates. She prefers to sleep all day inside their tower, where it's safe. Except it isn't any more. Strange plants have started to take over and tower blocks are falling down around them. Now Ade and his mum are trapped and there's no way out . . .