As she returned downstairs, she saw two doors to her left that she hadn’t noticed before and wondered if there might be anything worth investigating in them.
She turned the handle of the left-hand door. Just as she did so, a voice behind her made her jump.
"I shouldn’t go in there if I were you."
Harriet turned to see a girl standing behind her, a little younger than herself.
She was dressed in expensive, if rather old-fashioned, clothes.
"Hello there," said Harriet with her most winning smile. "What’s your name, then?"
"Olivia?" said Harriet. "That’s a pretty name. Well, I’m sorry, Olivia. I’m afraid I was lost."
"Lost?" said the girl with a little snort. Harriet did not much like her tone.
"Yes," said Harriet. "But the door was locked. I see now I came the wrong way."
"The door is not locked, miss," said Olivia, stepping closer in a way that Harriet found unaccountably threatening. "It is blocked. We call it the Un-Door."
"The Un-Door?" said Harriet.
Olivia nodded, smiling even more. "That’s what we call it," she said.
"Because it’s a door, but it’s not a door."
— Uncle Montague’s Tales of Terror, Chris Priestley