Two men in a smoking-room were talking of their private-school days. ‘At our school,’ said A., ‘we had a ghost’s footmark on the staircase. What was it like? Oh, very unconvincing. Just the shape of a shoe, with a square toe, if I remember right. The staircase was a stone one. I never heard any story about the thing. That seems odd, when you come to think of it. Why didn’t somebody invent one, I wonder?’