The PCs accidentally trigger an ancient whatchamacallit and the entire house (along with all its contents, such as PCs) gets plane shifted to (The Astral Plane / The Plane of Shadows / The Plane of Dreams / Baator / The Abyss / A Pocket Dimension / Carceri / The Far Realms / Other). Now they have to deal with getting back and get the additional problem of whatever beings are waiting for them in their new location (including the guy who set up the trap to begin with).