Mysterious lights are seen in the sky over famous UFO hot-spot Cooper Hill. When a local forest ranger suffers a strange death, the visiting UFO spotters are convinced aliens are responsible. DCI Barnaby and DS Nelson unearth suspicions, betrayals, and long-buried secrets in their search for the truth, centering on the nearby RAF base, including events going back over 20 years when secret research was conducted on aerial spying equipment, and there were secret affairs between villagers and RAF personnel. Guest stars Lee Armstrong (Call The Midwife) and Alison Steadman (Gavin & Stacey).
