You are attending a halloween party, and you're bringing some pretty scary guests: a vampire, a witch, a goblin. You're also bringing a pumpkin.
Along the way, you must cross a river. There is a small boat available, but it's only large enough to carry you, the pumpkin, and one of your guests. You can't leave the goblin with the pumpkin (he'll eat it). You can't leave the witch with the goblin (she'll cast a spell on him). And you certainly can't leave the vampire with the witch (he'll drink her blood).
Despite these restrictions, it's still possible to cross the river. You will need to make several trips, bringing one of your guests across, and sometimes bringing one back. Figure out how to ferry your guests across the river without any unfortunate mishaps. Tell me who is in the boat (with you) each trip, and who is on each shore.
You should work with a partner ... this problem is too scary to do alone!!