On October 27, 1974, John and Elaine Avis and their three children were driving home through Aveley, Essex, when their car radio sparked and a thick green mist enveloped the road. They arrived home with roughly two hours unaccounted for. Under hypnotic regression conducted by investigators, each family member independently described being inside a large vessel with tall humanoid beings.

British ufologist Andrew Collins led the investigation, publishing a detailed case report in Flying Saucer Review in 1978. Collins called it 'probably the most important British [abduction] case ever.' The family had no prior interest in UFOs and reported marked personality and behavioral changes following the encounter, including altered dietary habits and heightened environmental sensitivity.