Spark's investigators work through the cases that built modern UFO lore, from close encounters to abduction claims, testing each against mundane explanations. The film revisits famous sightings and asks whether witnesses saw genuine anomalies or misread aircraft, weather phenomena, and psychological pressure. Interviews and archival photographs anchor the discussion as researchers weigh eyewitness testimony against radar records and physical evidence where it exists. Rather than treating every claim as equally credible, the film separates cases with plausible conventional explanations from the handful that investigators admit remain genuinely unresolved. It covers the pattern common to abduction accounts, the role of memory and suggestion in shaping them, and why certain sightings became cultural touchstones while others faded. The tone stays skeptical without dismissing the subject outright, presenting the appeal of the phenomenon alongside the scrutiny it deserves. By the end, the film leaves a short list of sightings that still lack a satisfying earthbound explanation, framing them as the genuine mysteries rather than the debunked majority.