TARDIS: "The sound built slowly.  It was rhythmic, pulsing, grating, and seemed to tear the fabric of the very air.  It was as if it came from the walls of the room, out of the air, from no one discernable point in space but from everywhere.  Pickering slowly stood up, looking round for the source of the sound and failing to find it.  A patch of dark on the wall caught his attention.  At first it was the barest hint, the intimation of a shadow.  Then as Pickering watched, the shadow slowly solidified, pulsing darker in time to the grating sound.
    He checked the machine pistol and took cover behind one of the consoles as the shadow solidified, became a dark blue.  In a moment it had taken on the form of an obsolete police telephone box, the light on the top flashing in time with the unearthly noise.
    Then, with a thump as solid as the police box had become, the noise ceased.  The light went out and the door opened."