Episode 1
The Doctor, Jamie and Victoria are taken prisoner by the staff of a gas refinery, who have lost contact with their drilling rigs and experienced mysterious drops in pressure.
Episode 2
As the situation worsens at the refinery, Chief Robson refuses to halt the gas flow. Elsewhere, the weed extends its influence and Mrs Harris receives sinister visitors.
Episode 3
Despite the mounting evidence, Chief Robson refuses to acknowledge that matters have escalated beyond his ability to control them.
Episode 4
Investigating the impeller shaft, Van Lutyens is overwhelmed by the weed creature. A call comes from one of the off-shore rigs - the weed creatures are attacking and taking over!
Episode 5
As the weed breaks into the Pipeline Room at the refinery, the deranged Chief Robson kidnaps Victoria in a helicopter and heads for the Control Rig.
Episode 6
The Weed has complete control of Chief Robson and threatens to conquer Earth. The Doctor searches for a means to defeat the creature and believes the answer may be Victoria...
