UFO reports go back more than a century, but this Naked Science episode picks three of the most argued-over cases and tests them against physics rather than folklore. It revisits the Rendlesham Forest incident in a Suffolk woodland where military personnel reported lights among the trees, the 1997 Phoenix Lights witnessed by thousands across Arizona, and the 1947 Roswell crash that started the modern UFO era. Physicists and astrophysicists work through whether interstellar travel is plausible at all, weighing wormholes and warp drives against the sheer distances involved, and one researcher raises the alternative of self-replicating nanobots doing the traveling instead of crewed craft. The film also sits with a self-described abduction experiencer who says she was taken from her bed and examined, then turns to a neuroscientist offering a physiological explanation for that kind of memory. Michio Kaku appears among the scientific voices asked to weigh the evidence. The film keeps its questions open rather than pushing a verdict: could any of this be real, and if not, why do the accounts feel so consistent?