An Elder God, a being adrift in a different dimension, has reached out into their minds, giving them the knowledge needed to awaken it and bring it into our own world, freeing its hellish powers on the unsuspecting populace. Far to late the Investigators find out about it. The final ritual has started. But with a bit of luck, the god may just be vulnerable for a moment after being summoned. That is when they can shoot it in the face.