In a remote valley in central Norway, unexplained lights have been reported for decades. During the early 1980s, sightings became so frequent that residents sometimes reported luminous objects several times in a single week. Unlike many unexplained aerial phenomena, Hessdalen eventually became the subject of organized scientific observation. ([Project Hessdalen][1])

This episode examines what witnesses reported, what Project Hessdalen actually measured, and the natural explanations proposed by researchers. Cameras, radar, spectrographic equipment, and other instruments have recorded unusual events, but scientists have not reached a single accepted explanation for every observation. ([Frontiers][2])

Are the Hessdalen Lights several ordinary phenomena being mistaken for one mystery, or is something unusual still happening in this Norwegian valley?