While out hunting with Veronica, Roxton accidentally shoots a young woman who appears suddenly in a flash of light. Returning to the treehouse, Summerlea helps Roxton nurse her back to health. Meanwhile, Marguerite, Malone and Challenger discover a tablet that points to a possible way off the plateau. After making their way to some ancient ruins, the trio are attacked by armed warriors but a stranger arrives to help fend off the attackers. As events play out for the two groups, the two mysterious new arrivals tell separate tales of what they are doing on the plateau. They both purport to be from the future and Marguerite is the focus for each of them - one wants her dead to stop her unleashing a deadly plague, while the other wants to ensure she returns to London.