Betrayal at House on the Hill is a board game published by Avalon Hill and designed by Bruce Glassco. Players all begin as allies exploring a haunted house filled with dangers, traps, items and omens. As players explore the mansion, new room tiles are chosen at random; accordingly, the game board is different each session. Eventually the "haunt" begins, with the nature and plot of this session's ghost story revealed; one player "betrays" the others and takes the side of the ghosts, monsters, or other enemies, while the remaining players collaborate to defeat them.