The water supplies go off. Mike tells Liz his experience with the "winking" keyhole and from this she decides that Martyn must have bugged the main room but not the bathroom area where Mike and Liz have been talking.
The water supply is interrupted. Mike describes his encounter with a "glaring" keyhole, causing Liz to infer that Martyn likely placed a listening device in the main room but not in the bathroom area where Mike and Liz were communicating.