Back in the early 80's during the hight of the video game craze, there's an urban legend about the video game Polybius. It supposedly gave people who played it nightmares and suicidal thoughts, and it shortly disappeared after it's release. Some claimed it was a secret government experiment, maybe it's origins are even more sinister. This scenario would probably work better with a UNIT or Torchwood based campaign.
The players have come to Silicon Valley in the early 1980's to look into some strange incidents involving young people. Many have disappeared, and some have turned back up in catatonic states. A little research on all the victims discovers they were all avid video game players, and this new game that’s showed up around town, Polybius, has been the big attraction for all of them. Talking with the players at some of the arcades, the kids mention the game seems to disappear pretty soon after they show up. They think it's their parents complaining and the owners pulling the machines. Except the owners of these arcades have never heard of these machines! If you use the arcade player grapevine, you soon find a machine, and the owner of the arcade is wondering where it came from. If you can convince the owner to let you take a look inside the machine, things suddenly get out of hand, the game unit's screen starts making a pulsing glow, and attacks with an electrical blast. Then it just teleports away, leaving the injured and confused.
WHAT'S GOING ON
The Polybius is an alien computer. It was a tyrannical central authority on it's home world, and controlled through it's merciless iron will. Finally the people of the world rallied together to try and remove the machine, but before it was
overthrown, it launched a massive number of Nodes out into the stars, planning on spreading it's power off world.
Landing on Earth, it found humans easy enough to control, but it needed more computing power and energy to truly take over.. It was able to establish itself within a company making arcade games, and began building nodes within their games to help increase it's control and power. The Nodes have been hypnotizing the gamers (especially the highly successful ones) and having them come to the factory. Polybius is using their brains as organic computer power to help expand it's abilities and build more Nodes.
It's objective is conquest of the planet, it wants to establish control through it's hypnotizing Nodes and systematically incorporate everyone into it's network. At least those it can use, otherwise they end up catatonic like some of the kids.
THINGS TO DO
Track down the Polybius factory. Free the people under it's control, and figure out how to shut it down.
The Polybius Computer is stationary and defenseless, but it's Arcade Game Nodes can teleport freely and can either use it's screens to try and hypnotize or attack. It should almost be like the Weeping Angels movements, literally appearing out of nowhere with the glowing screens throbbing menacingly.
The kids at the arcade that know what's going on. Maybe a PI who's been hired by the parents to find their missing child. Maybe some of the aliens from it's home world have arrived on a mission to ensure it's eradication.
A running fight within the highly automated Polybius factory.
Figuring out a way to free the hypnotized people from the Polybius control. Shutting down the main computer and interfering with the Node teleport signals.
CONTINUING THE ADVENTURE
This wasn't the only Node released, it may be encountered elsewhere.