Absolute Blockade

The group is finally able to get to the main gate of the base, and they're glad to see that the weapons are there. They're going to use them to get out of the way of the horde of undead that's trying to get through the gate. As they run, they hear the sound of a huge explosion. The group realizes that it's the main entrance to the base. They unlock the door and find that the main room is actually the central control room of the whole base.