Rover (The Prisoner)

Rover
The Prisoner television series element
Rover, shortly after rendering Number Six unconscious on the beach outside the Village.
First appearance

Rover is a plot device from the 1967 British television programme The Prisoner, and was a crucial tool used to keep 'prisoners' from escaping the Village. It was depicted as a floating white balloon that could coerce, and, if necessary, incapacitate or kill recalcitrant inhabitants of the Village. It also had the ability to subdivide. Several aspects of the Rover device were left unexplained and to the imagination of the viewer.

The name "Rover" was only used once in the entire series (in the episode "The Schizoid Man"). The novel The Prisoner: Number Two by David McDaniel, based upon the series, uses the name Guardian.