“The Sound of Silence” is episode twenty-three of season one of UFO.
A probe is travelling through space when SID reports a UFO sighting. Interceptors are launched and the probe, GSP-4, contacts Houston and talks about a strange signal they’re recording.
At SHADO Control, Straker wants a press blackout about the signal. The UFO is getting close to the GSP-3. Too close; the Interceptors are in range, but if they fire, the manned probe will be destroyed. They are recalled and Skydiver alerted as the UFO follows the GSP-4 to Earth.
A man and a woman are on horses; the woman falls off hers when Sky 1 passes overhead. Sky 1 reports no sign of the UFO in the area and is recalled, with Mobiles dispatched.
Another man is in the woods at a shack when his dog barks. He goes looking with a knife, but doesn’t see the alien watching him. The riders hear the dog bark and go looking. The male rider, Russ, knows the man, Culley, and runs him down, telling him to get off their property.
The Mobiles arrive in the area as the alien is watching the house. Inside, Russ, his siter, Anne, and their father are talking. Russ doesn’t like Culley and thinks he’s dangerous. The other two don’t seem that bothered. Russ says if the police don’t do anything about Culley, he will.
Culley’s dog barks at the water, but he can’t see anything. After they leave, there’s a glow from the water.
The Mobiles haven’t found the UFO and Culley decides to head for the house. He enters the stable and upsets the horse. Anne goes to check as Culley is watching her. Her brother joins her as Culley watches. After they leave, Culley is killed and dragged off.
Though Culley may have been dangerous, there is something more dangerous than him. The Mobiles can’t find the UFO, but when Russ goes missing, Straker suspects the aliens are in the area.