The Tomorrow People - Season 2 - Eps 5: The Blue and the Green, Part 5: The Swarming Season
Robert explains to John that his race uses violent energy as a power source. If they stay on Earth, they will die, but the violence needed to power their departure will completely destroy Earth's civilisation.
About The Tomorrow People

Title: The Tomorrow People
First Air Date: 1973-04-30
Last Air Date: 1979-02-19
Status: Ended
Rating: 6.6/10 (from 11 votes)
Language: EN
Seasons: 9
Total Episodes: 68
Network: ITV1
Genres: Sci-Fi & Fantasy, Drama
Production Companies: Unknown
Synopsis
Born to human parents, an apparently normal child might at some point between childhood and late adolescence experience a process called 'breaking out' and develop special paranormal abilities. These abilities include psychic powers such as telepathy, telekinesis, and teleportation. However, their psychological make-up prevents them from intentionally killing others.
Cast

Nicholas Young
John