Stalker

The term stalker characterises one who has an intense voyeuristic obsession with a particular person. This obsession leads them to physically follow a person from place to place and observe them.

Stalkers most commonly attempt to remain hidden from their victims.

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Stalker is also a film by Andrei Tarkovsky. See Stalker (movie).

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Stalkers are also the protagonists of The Whispering Vault roleplaying game.