Luna did not expect to be pulled into a memory when she consented to being "shown" the answers to her questions.
All the same, soon she found herself in free-fall, her skirt flying up around her torso so that she had to assume Marilyn Monroe position in midair (Marilyn Monroe was a Muggle about whom Luna knew plenty, because Marilyn Monroe had had a secret affair with Gellert Grindelwald, leading ultimately and tragically to her demise. Not that most wizards would admit this.). Then there was marble floor under her, and she was on a dark street, in front of a shop that said Borgin & Burkes.
Beside her stood Tom, albeit his sixteen-year-old self.
"This is Knockturn Alley," Luna observed.
Tom did not speak. He gave no indication that he had heard her.
"What am I doing here?" Luna persisted.
Instead of answering, Tom walked through her. He just...walked through her, as if he were a ghost, or as if she were. He entered the shop without looking back to see if she was following.
Of course she was supposed to follow, since this was the scene that Tom was showing her to answer her questions.
But Luna was curious. Instead of following Tom into the shop, she walked further down the street. As she walked, the setting darkened, until it was pitch black and silent and all she could sense was the ground beneath her. Then even the ground left, and she was suspended in darkness.
What are you doing? The words scrawled themselves into the darkness in white ink. Somehow, they tasted of irritation.
"I wanted to see how far the memory goes," Luna answered aloud.
Why? I thought you wanted an answer to your questions.
"I became a bit distracted, I suppose. I was curious. This is an odd sort of magic, you know."
Instead of answering, Tom changed the setting: he placed her in a room that she instinctively knew was behind the shop. Also in the room were Tom, the greasy shop owner, and a lean man dressed in the attire of a Ministry employee. Not just any employee: he looked as though he was from the Department of Mysteries.
"So you tell me," the shop owner drawled to the Ministry man, "that you cannot pay your debt?"
The Ministry man had a scornful look. "Surely you can overlook a few stray Galleons."
The shop owner shook his head with a terrible sort of smile. "Riddle, read off Mr. Mulligan's history of purchases."
With a flourish that caused Luna to laugh a bit (not that anybody in the room was in a position to notice), Tom unrolled a scroll and began to read off: "Dragon loin, splinching cloak, skin removing powder, throat of-"
"Alright, alright," the Ministry man, Mulligan, interrupted. He had gone more and more ashen-faced as Tom read.
"Quite a sum," the shop owner surmised. "Pity if such an incriminating list were to fall into the wrong hands."
"I can't pay," Mulligan insisted. "What do you want from me?"
The shop owner scratched his chin. (Luna wished she had her spectre-specs; she wondered which person in that room had the most wrack spurts.) "Oftentimes goods can be redeemed for services," the shop owner mused. "The Department of Mysteries is an interesting place indeed. Do you have any secrets that would be worth, to me, what the secrets in Tom's hand are worth to you?"
Mulligan looked reluctant, but still he leaned forward and whispered to the shop owner (and consequently to Tom, who was trying to pretend that he wasn't listening nearly as closely as he was), "They've cracked time travel."
"Who has?" the shop owner asked, a greedy glimmer in his eyes.
"The Department," Mulligan replied. "They've made a sort of...necklace that can send one back in time. We call them time turners."
The shop owner began to grin widely.
"This cannot become common knowledge," Mulligan insisted. "The use of such tools would have guaranteed unforeseen consequences."
"It's a pleasure doing business with you, Mr. Mulligan," the shop owner said, still with that awful grin, and Tom took his cue to escort a flustered Mulligan out.
Then Luna woke up in her spot on the Hogwarts grounds, in the grass with a baby thestral nudging at her ankle and Tom's diary under her face, open to a deceptively blank page. She found her quill beside her, dipped it, and scrawled out, That didn't answer much.
Didn't it? I've given you a way to come see me without the Doctor's help.
Luna went still.
Tom wrote again: You don't want me to be alone, do you? You're the only one I trust.
Luna traced the word trust.
Tom's next message was concise: Do you trust me?
That's a silly question. That's not even the point. Whether I trust you or not, how would I acquire a time turner?
I already acquired it. You would only have to retrieve it.
Where is it?
Say you trust me. Say you won't tell the Doctor. Say you'll come straightaway.