 The Doctor is aware the Sontarans will not concede defeat but feels that he needs to give them a chance to withdraw.He teleports to the Sontaran ship and offers Staal the chance to retreat, but Staal calls the Doctor's bluff and encourages him to destroy them.Humbled, Rattigan reactivates the teleport and switches places with the Doctor, sacrificing himself to activate the device and destroy the Sontarans.