Masen rescues a schoolgirl named Susan (Janina Faye) from a crashed train; she has no parents and is a ward of the state. They decide to leave London and head across the English Channel to France. Masen and Susan find refuge at a chateau but when it is attacked by escaped sighted convicts, they are again forced to escape; shortly afterwards, Triffids attack forcing everyone in the chateau to flee and eventually make it to safety onboard a submarine. The carnivorous plant population continues to grow in number, feeding on people and animals as they move.