Horizon investigates claims of signals from extra terrestrials. In 2006, Duncan Lorimer and Maura McLaughlin discovered a enigmatic signal from space, known as a fast radio burst. It was a pulse of radiation so bright, it didn't appear to be caused by any known object in the universe. Explanations ranged from colliding neutron stars to communication signals from an alien civilisation. Scientists have been searching the cosmos for strange signals like the 'Lorimer Burst' for more than 50 years, ever since astronomer Frank Drake convened a secretive meeting of a group of scientists calling themselves the 'Order of the Dolphin'. The film ends with scientists latest search for extra-terrestial intelligence - Horizon obtained exclusive access to film researchers at the Green Bank Telescope searching for radio signals from 'Tabby's Star' - a star so mysterious some scientists believe might be surrounded by a Dyson Sphere - a vast energy collector built by advanced aliens.