Luna Lovegood was not asleep. She had been in bed, the new issue of Magical Creatures Monthly on her lap, when it had occurred to her to put on a pot of Gurdyroot tea. One would want tea on a night like this. She slipped into her bright yellow housecoat and fuzziest slippers, and padded down the stairs to the kitchen. Something in the air had shifted, she mused, as she poured the boiling water over the roots. She arranged a few biscuits on a plate, for good measure, then went to answer the door.

Ron started as the door swung inwards with his hand still on the knocker.

"Oh, hello," Luna answered in her sing-song way. She wore her blonde hair in two loose plaits. She did not look surprised to see them.

She ushered them into an odd trapezoidal sitting room, which held slightly too much furniture for a room of its shape and size. It reminded Hermione of the Gryffindor common room, with its mismatched armchairs, cozy in its disarray. Hermione chose a Louis XIV Bergère, Ron a piano stool.

"It's good of you to have us, Luna." Hermione's eyes darted uncomfortably around the room, unsure of where to settle. For all Luna knew, they hadn't spoken properly in years, save small talk at a few Ministry functions, and even at Hogwarts they had never been close. Hermione had no way of knowing that this woman would even believe her, let alone be able to help. But Luna had once fought at her side, had chosen the right path over the easy one, had helped knit her bones back together the night they destroyed Helga Hufflepuff's cup. That bond meant something, whichever reality it existed in. All the same, it had been an impossibly long night, and she grew weary at the prospect of explaining everything from the beginning.

"Not at all," Luna crooned. "I assume this is about the timeline?"

The Department of Mysteries had begun to suspect that something may be out of kilter a few years ago, but even with the top Unspeakables working 'round the clock, they had arrived at no explanations. The 'temporal hiccup', as it had been dubbed, had even the department's best minds stumped. Luna herself, though only a junior member of the department, was known as something of a prodigy in temporal theory, and had been brought in to work on the problem.

As inhabitants of the time continuum, she had explained to the Minister's cabinet, they had no way of knowing what had been changed. Ordinarily, of course, this wouldn't pose a problem. The continuum shifted trillions of times a microsecond, each decision and whim of every witch, wizard, Muggle, and Flobberworm swinging it wildly in all directions. Would Mrs. Jones eat oatmeal for breakfast today? Yes! And bang! The doors to myriad possible worlds slammed shut. Egg on toast, kippers, beans and sausage; none of these were to be had today. The world ticked on, no-one the wiser to what might have been had she instead smeared marmalade on a muffin.

In this case, though, they were aware. Maddeningly, each of their best instruments, calibrated and recalibrated for the thousand-and-fourth time, registered a fraction of a unit off.

The mystery, then, was not so much why the timeline had changed, but why they could tell. The best her team could surmise was that when this particular variation in the continuum had occurred, something, however minute, had been left out of the change.

"Until tonight, I had no idea what that might be," Luna continued, "but I had a funny feeling this evening…and when you showed up, I had a feeling you might have picked up on something as well."

Hermione retold a hurried version of the events of the past few weeks, grateful for Luna's open face and unabashed acceptance of impossible truths.

"I know it's difficult to believe- I have no way of proving that these memories are anything more than dreams," she continued, frustrated.

"I have an idea." Luna stood swiftly and disappeared down the hall. Ron looked incredulous.

"Care to fill us in?" he inquired after her retreating figure. "Blimey, hasn't changed much, has she?"

She reappeared a few minutes later with a large painting in an ornate frame. She presented it triumphantly to Hermione, who held it in her lap uncertainly.

"Er, thank you," she stammered.

"What do you see?" she asked, neutrally.

Hermione examined the painting. "Woods," she began, "with a little cabin at the- oh! It's Hagrid's cabin; it's the Forbidden Forest!"

Just then, she noticed a rustle in the depths of the tableau. She held her breath as a dark shape emerged from between the trees- a dark, skeletal horse, with leathery wings, beautiful and dreadful.

"Thestrals," she breathed.

Luna nodded.

"And, have you ever-"

"No," said Hermione softly. "I… not in this timeline. But I – in the other one – Fred…" She trailed off, paling. Ron too, looked slightly ill, but gripped her hand reassuringly.

"So I'm really… I really was there." She took a sip of tea, and, concealing a grimace, placed the cup delicately back on its saucer.

"The funny thing is, though," she mused, "I can't remember anything after our seventh year- well, what would have been our seventh year."

"Maybe that's got something to do with how it… changed," suggested Ron.

"Hm," agreed Luna, "What's the last thing you remember?"

"I…" Hermione searched her memory. "We had found the last Horcrux. We were going to destroy it but they – the Death Eaters – they got there first. There was a battle, and…"

She shook her head, frustrated.

"It's no use, everything's so muddled!"

Luna stood again, beckoning to them from the doorway.

"Follow me."

From the hall, she led them down a set of stone steps and through the arched door at the bottom. The room was surprisingly warm; Hermione had expected it to be chilly, given its marble construction. She moved against the wall to allow Ron to follow her into the chamber. Taking up most of the floor was a large stone pool, like the base of an ornate fountain. Hermione held her breath. It was the largest Pensieve she had ever seen.

"My work gets a bit tricky to sort out, sometimes," offered Luna, by way of an explanation.

Hermione set to work, her wand against her temple, a look of deep concentration etched on her face. Slowly, after a minute or so, she pulled a long, silvery filament into the pool. Leaning forwards, they tumbled through the basin into the dark night.

They watched as a younger Hermione ran haphazardly through the foggy graveyard, curses ricocheting wildly in every direction. Ron reached out instinctively as she hurtled to the ground, tripped by a stray root, but of course, she couldn't see him. There, not twenty feet away, were Harry and Voldemort, locked in battle. A silver filament bound their wands together, pulsing with green and gold beads.

It was then that she saw the eyes – those horrifying reptilian eyes – gleaming … and the thin, sickly lips, stretched into a hideous mock-grin across the pallid skull of a face, moving almost imperceptibly, whispering… whispering what?

"Aevum retexo!" The green bead pulsed and shuddered as it forced its way down the golden filament. It was almost at the tip of Harry's wand, and then-

The world tilted on its axis. Hermione's entire field of vision was awash, was melting into itself.

"Protego!" She heard herself shriek amidst the din.

Ron, Luna and Hermione found themselves jerked disconcertingly from the memory, as the mossy ground solidified instantly to marble.

"That's it," Hermione whispered incredulously. "That spell- that's how it started."

Ron exhaled shakily, wide-eyed.

"Right. Now what?"

"We go back. We go back and we fix it. We stop Voldemort from casting the spell, and-"

Ron gaped.

"Stop You-Know-Who? You said it yourself, love, most evil man in the history of wizardkind. How are we supposed to stand half a chance against that?"

She didn't have a chance to answer.

"I don't think we'll have that option," said Luna, who had stayed quiet until then, deep in thought.

Hermione looked up, her face stony with realization.

"You're right," she whispered. "We can't. We can't go back and change it because it isn't really the past. That never really happened, at least not in this reality." She looked utterly defeated.

"No," agreed Luna. "But there may still be something we can do." Ron and Hermione looked up at her expectantly.

"Get your coats," she continued, "we're going to the Ministry."