Space Security Service

Space Security Agents were members of a special force used in the 41st century to gather intelligence relevant to the safety of the Solar System and, when necessary, eliminate threats to that safety. Among these agents was Marc Cory, who discovered a plot by the Daleks to convene an alliance of alien powers on the planet Kembel for an attack on Earth, but was killed before he could send warning to his homeworld. Another was Bret Vyon, who arrived on Kembel months later to investigate Cory's disappearance, and learned of the Dalek plot and more importantly that Mavic Chen, Guardian of the Solar System, had betrayed Earth and allied himself with the Daleks. Vyon allied himself with the Doctor in his efforts to warn Earth but was later killed by his own sister, Sara Kingdom, yet another agent. Kingdom had been told by Chen that her brother was the traitor, but upon learning the truth she too agreed to help the Doctor fight Chen and the Daleks.