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's happier sleeping all day inside their tower, where it's safe.

But one day, other tower blocks on the estate start falling down around them and strange, menacing plants begin to appear.

Now their tower isn't safe anymore. Ade and his mum are trapped and there's no way out . . .