Many UFO sightings have been dismissed as the products of unreliable witnesses or hoaxes. But a few are harder to explain. INVASION EARTH retells and reconstructs incidents from all over the world. With the help of a panel of experts, all the evidence is tested. In this episode, Canadian villagers see a string of lights crash into the ocean, sparking a major investigation. In New Zealand, a mysterious object streaks across the country in broad daylight - but what is it? And in Iran, jets are scrambled to deal with a brightly coloured UFO, leading to an astonishing dogfight.