Thingumajig: Avengers (TV Episode)

Plot

During the excavation of an old Norman church, several top archeologists are killed. Upon further investigation, Steed and Tara discover that the dead men had been sapped of all their energy. The cause of this phenomenon is a tiny black box containing a deadly supercharge of electricity, which in turn has spawned a race of omniverous pure-energy creatures, bent on destroying all of England. Written by Terry Nation, "Thingumajig" first aired in America on March 24, 1969, then in England on April 2 of that year. ~ Hal Erickson, Rovi