A meteorite hits the North Sea near an oil rig. The oil rig survives the shockwave, but on the sea floor the meteorite glows ominously. The Doctor and Miss Young arrive in Bessie at a government research laboratory in Scotland, where he has been summoned by his old friend Professor McBane. McBane introduces them to Karl Moreton of Bentick Petroleum. They take a helicopter to the oil rig, where large pink tentacles attack a fire fighting vessel. The Doctor takes a sample of the pink substance back to the laboratory. He discovers it is seaweed contaminated from radiation from deep space brought by the meteorite. Furthermore, the mutated seaweed is attracted to sound, so the sound of the oil rig puts it in danger.