So there is 1 spy (or whatever you want to call him) and multiple guards (rest of the people on the server)
The guards are spread throughout the base, guarding certain areas and are not allowed to leave that area, and the spy has to get through all the guards and arm a bomb in the middle of the base.
Its basically a 1 man army with the odds in favor of the guards. The spy has to be stealthy to kill the guards and get to the bomb.