The nine o'clock horses

From Folklore of Leicestershire and Rutland by Roy Palmer:

By far the most widely used threat was that of the nine o'clock horses which would mangle young children who were out too late, or even staying up too late. In some places they were called bell horses, which might indicate that the fear was originally connected with the curfew bell, which once rang at nine o'clock.

I offer "The Nine O'Clock Horses" as the title for a novel or poem.