Editing Big List of RPG Plots (section)

== Pandora's Box ==

Somebody has tinkered with Things Man Ought Not, or opened a portal to the Mean People Dimension, cracked a wall at the state prison, or summoned an ancient Babylonian god into a penthouse. Before the PCs can even think of confronting the source of the trouble, they must deal with the waves of trouble already released by it: monsters, old foes out for vengeance, curious aliens who think cars/citizens/McDonald's hamburgers resemble food, and so forth.
* The PCs can't simply take the released badness to the mat; they have to collect it and shove it back into the source before it the adventure can really end. 
* The PCs are drawn in to the source and must solve problems on the other side before returning to this one. 
* A secret book, code, or other rare element is necessary to plug the breach (maybe just the fellow who opened it). 
* A close cousin to this plot is the basic "somebody has traveled into the past and messed with our reality" story.