This is a stock plot designed to force the characters or players to stay in a location and get involved in the adventure... and not be able to leave until it's done. The variations on this set up are nearly limitless, and can work in pretty much any and every genre or setting. The classic set up though is as follows: The heroes are driving along, when all of a sudden what should happen but an inconvenient flat tire. Unfortunately, the spare is flat too, the rain is coming down, and of course it's also thundering. There's no choice but to stay at the Haunted Castle until the weather clears. Lo and behold, the Mad Scientist living there has just reached the critical phase in his breakthrough in Necro-Botanics, and of course something goes horribly wrong and the undead Venus flytrap gets loos