Description
Jeff and Frankie Callum run The Swan, an inn on the island of Fara, somewhere off the English coast. Jeff, a professional novelist, hires a secretary, but this turns out to be Angela Roberts, a younger woman with whom he had an affair some time before, and who has come to the island with the intent of luring Jeff away from his wife, or at least causing trouble in their marriage. The Callums moved to Fara so that Jeff could escape Angela's amorous advances, although as far as Frankie knows, it was only to escape the tedium of life on the mainland.
Not helping matters is the fact that despite it being the middle of winter, Fara is experiencing a stifling and inexplicable heat wave, with temperatures rising rapidly. It has become so hot that cars stall, beer bottles shatter, televisions explode, and telephones have ceased to work.
Into this tense situation comes Godfrey Hanson, a mysterious scientist from the mainland, who rents a room at The Swan. Hanson spends his time exploring the island, setting up motion-sensitive cameras and taking soil samples. The locals, including the Callums, find this suspicious, especially since quite a lot more is happening on Fara than just the heat and Hanson's snooping.
A tramp is burned to death in a cave by something emitting a high-pitched whirring sound. Later, a farmer claims his sheep are all dead. Hanson examines the dead sheep and finds their corpses are badly burned, whilst Swan regular Bob Hayward is attacked by something on the road while driving into the village. He crashes after being blinded by a bright light, which also creates enough heat to ignite the car's petrol tank. Meanwhile, pub regular Tinker, losing his mind because of the heat, attempts to attack Angela whilst she's working, but when she hits him over the head with an ashtray, he flees and ends up burned to death as well. Jeff finally confronts Hanson and demands answers from him. According to the scientist, Fara is the site of an invasion by extraterrestrials, whose extremely high temperature burns any living creature that gets too close to them.
Jeff and Hanson resolve to stop the aliens with the help of local physician Dr. Stone, but when Stone tries to get to Fara's meteorological station so he can alert the mainland of the invasion, he is waylaid by the aliens and killed. Hanson tries next, but witnesses the death of Stella Hayward, Bob's wife, and realises the aliens are attracted to light. At the weather station, he learns from meteorologist Ken Stanley and his colleague Foster that the aliens have already destroyed all their communications equipment, making it impossible to call for help.
Quickly formulating a plan, Hanson is joined by Jeff, Frankie and Angela at the radar station. He and Foster will set fire to bales of hay in a field, attracting the aliens, and then lob dynamite into the field, hopefully destroying them, whilst the others signal for help with flare pistols.
This plan quickly fails, and Foster and then Hanson are both killed. Surrounded by the deadly aliens, the situation looks hopeless when a sudden thunderstorm breaks. Unexpectedly, the rain brings death to the aliens, and Jeff, Frankie, Angela and Ken all survive.
