Kneeling on the floor in the ante-room the girls watched Miss Renton unpack some further treasures, then held up the lids of the show-cases while she bestowed them in their due places.
"It's quite nice to have two assistant museum-keepers," she laughed. "These great glass lids are so heavy I never dare to lift them without someone to help me. If one dropped back there would be a smash."
At last everything was arranged, the cases were locked, and the keys returned to Miss Renton's bag. She put on her waterproof, took her umbrella, and prepared to leave the museum. But when she tried to open the old oak door it was fast shut. She turned the ancient handle and tugged and pulled, but all in vain. Then the horrible truth burst upon her.
"We're locked in!" she gasped.
There was no possibility of doubt about it. It was quite easy also to see how it had happened. When the museum was on view the door was propped open to admit the public, the curator always shut it before she left, and as she walked across the courtyard of the Guildhall would ring the caretaker's bell, as a signal that the place might be closed.
To-day the bell had been broken, and the caretaker, noticing the High School girls go away, must have come upstairs afterwards, and seeing the museum door shut had locked it, thinking Miss Renton had gone with the others. The three unfortunate prisoners were aghast. It seemed almost too bad to be true. They all tried the door in turns, they knocked, they thumped, and they called. There was no response except a dull echo.
"Why couldn't the caretaker look inside to make sure we were gone before he locked up?" asked Marion, half-crying.
"Perhaps he did, and we were inside the little oratory. It's my own stupid fault for shutting the door. I ought to have thought about it. It never struck me he might come upstairs and think we were gone."
"Will he be coming up again?"
"It's not at all likely. He's probably gone home."