The Federation have recently made contact with the Dolysians, a pre-warp civilisation who have colonised Gralafi, another world in their system which is hidden behind an energy shield which only opens for a short period every three years. The patrol ship USS Huang Zhong is carrying out a survey of the phenomenon when its warp engine and sensors trigger off an ancient defence system and a tractor beam causes the ship to crashland on Gralafi, killing most of the crew. The most senior of the survivors is former Enterprise officer Lieutenant Boma.