Somewhere in the south of England stands the Hothouse. Five vast, state-of-the-art biodomes, all steel and glass. Inside, rock star turned environmental activist Alex Marlow has a plan to save the world from climate change. By any means necessary...

There's something growing inside the Hothouse. Something that could turn back humanity's tide. A voracious alien vegetable called the Krynoid. The Doctor's going to have to stop it. Stop Marlow. Stop Marlow's fanatical acolyte, Lucie Miller...