Suddenly Nicky's foot, as she slid it carefully in front of her, met empty air. "Hi!" she said. "Wait! There's nothing here! It's, it's..." She explored cautiously with her foot. "I do believe it's the stair!"
They heaved great sighs of relief and started a careful descent. All would have been well if they had remembered that the Great Staircase had two bends in it. The first they negotiated successfully, but at the second they tried to go straight on when the stair turned to the left. They lost their balance, stumbled and fell and went clattering and tumbling to the bottom - as Lord Claire unlocked the great door and held aloft a storm lantern.
From NEW HOUSE AT NORTHMEAD, Chapter 11, Rescue.