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. But one day, other tower blocks start falling down around him. Strange, menacing plants begin to appear and no one knows where they came from. Now their tower isn't safe anymore. Ade and his mum are trapped and there's no way out.