Amy Pond has been kidnapped and the Doctor is raising an army to rescue her. But as he and Rory race across galaxies calling in long-held debts and solemnly-given promises, his enemies are laying a carefully concealed trap.

In her cell in Stormcage, River Song sadly acknowledges that the time has come at last. For this day will mark the Battle of Demons run and the Doctor's darkest hour. Both sides will make their sacrifices and River Song must finally reveal her most closely guarded secret to the Doctor.