Wishing Stairs

A staircase leading to the dormitory of a remote boarding school usually has 28 stairs, but every so often there appears to be 29. When someone steps on the mysterious extra stair, the horror begins
A staircase leading to a schoolgirls' dormitory usually has 28 steps, but sometimes a 29th step appears. Any wish you make while standing on this step comes true, even if it must come true in the most horrific way possible.