Martha Jones summons the Doctor back to modern-day Earth, but an old enemy awaits. With the mysterious ATMOS devices spreading across the world, Donna discovers that even her own family is not safe from the alien threat – but is it too late to save them?
Sunny and Bajie seek help from a reclusive former Master. The Widow must confront a spectre from her past as Chau's slave.
Sunny plays a dangerous game, causing his friends to question his loyality. The Widow discovers the existence of a new weapon as her alliance falters.
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.
