Sunny and Bajie seek help from a reclusive former Master. The Widow must confront a spectre from her past as Chau's slave.
Sunny and Bajie arrive at Pilgrim's Fortress, only to face an angry M.K. The Widow enlists Gaius. Moon and Lydia rally the troops.
Sunny plays a dangerous game, causing his friends to question his loyalty. The Widow discovers the existence of a new weapon as her alliance falters.
Martha Jones summons The Doctor back to modern-day Earth, but an old enemy lies in wait.