House of Silents (audio story)

 was the first story in the UNIT: Silenced audio anthology.

Publisher's summary
There is no record of the presence of an alien species known as 'The Silents' on Earth. UNIT has never engaged hostiles capable of editing themselves from observers' memories.

There is no evidence that such an opponent, if real, is regrouping and beginning a new plan of infiltration and manipulation.

Kate Stewart and her team are in no mortal danger. How can they be, when they don't even know the enemy exists?