A\N: Edited for better flow.
There isn't a Day Two of the Investigation of Tom Marvolo Riddle. Arthur and Kingsley decide re-establishing the Ministry and tracking down the remaining Death Eaters is their priority, and since they've squeezed out all they can from Tom Riddle in this regard, they save their interrogations for the other Death Eaters in captivity. A week passes, during which Harry lies awake at night turning the attic password over and over in his hands until he falls asleep. In that week Shell Cottage starts to empty as post-war life begins. Charlie leaves for Romania, and Hermione and Ron for Australia, to find Hermione's parents and bring them home. Of course they ask Harry along, but Harry senses they want this time to themselves, as a couple. So he wishes them luck, makes them promise to write, and sees them off as they Portkey to Melbourne. He thinks of moving out himself. Not that he isn't welcome here, but Ron and Hermione's absence remind him he can't stay indefinitely. Maybe he could move into his inheritance, Grimmauld Place, or sell the house (some blood purist family like the Malfoys would probably find it of historical interest and pay good money for it) and find himself a cheery, better-lit flat in London. Maybe. It's only when Mr and Mrs Weasley start talking about it being safe to move back into the Burrow soon and the Death Eaters being transferred to Azkaban that Harry makes up his mind.
He takes a satchel of food with him - leftover dinner, fruit, cakes, a tumbler of pumpkin juice… Filling it he feels a weird and unwelcome sense of deja vu, like he's visiting Sirius again in the days when Sirius used to live in a cave off Hogsmeade. The feeling hurts his heart, so he ignores it and clasps the satchel shut, pulls the invisibility cloak over his head, checks again that no one's stirred, disapparates.
Entering the Burrow is as easy as opening the front door and stepping inside. At first the house seems unnaturally quiet to Harry, but then realizes he's gotten used to the sound of the sea, ever present at Shell Cottage. Very slowly he crosses the kitchen and makes his way up the stairs, pausing every time the wood creaks beneath his feet before taking the next step. He's only a couple of steps away from the second floor landing when he comes face to face with Hagrid.
Hagrid is humming unsuspectingly. Harry is horrified. Throwing all caution to the wind, he ducks under Hagrid's arm and rolls onto the landing, landing with a thump. Hagrid stops humming. Looks suspiciously over his shoulder. Then, to Harry's relief, a Death Eater down the corridor starts thumping against his door and wailing loudly. Hagrid turns, the mystery solved in his mind, and continues down the stairs.
Harry hurries up the last two flights of stairs as quickly and as quietly as he can while he has the chance. "Grawp," he whispers to the attic door, and it opens for him.
Tom Riddle is not asleep. He's standing by the small attic window and staring out into the night.
"Is that you?" he asks softly, turning from the window when the door creaks shut behind Harry.
The invisibility cloak comes off.
"It is you," Tom says, stepping away from the window. He's silhouetted in moonlight and Harry can't see his face. "I'm glad I wasn't hallucinating."
Harry casts a quick spell on the door and the floorboards to keep sound from passing through. And then he says, "I brought food."
They sit by the tiny attic window and eat. Tom hunches over his food and eats very fast and doesn't bother with cutlery. He says they don't underfeed him here, but they've also never afforded him the luxury of cake or pumpkin juice or midnight snacks. When he's done he lays back and gazes out of the window, moonlight casting a dreamy glow on his pale face.
"Why were you awake at two in the morning?" Harry asks, settling back against the wall.
"Insomnia," Tom says, and Harry notes the dark rings below his eyes, "Terrible condition to have when you're in captivity and the only release from boredom is sleep." He sweeps his silky dark hair off his forehead and rakes his fingers through it. "Have they decided what they're going to do with me?"
"Well from what I overheard I think they might move you to Azkaban soon-" fingers tighten around waves of dark hair - "but only until you're tried."
Tom makes a strange noise, somewhere between a snort and a whimper. "Can you imagine them letting me go, Harry?" he asks.
Harry is silent.
"Of course not, people want blood and the last thing a newly established ministry will do is lose their popular appeal by granting me amnesty."
"It's the Wizengamot that's trying you, not the Ministry," Harry puts in.
"Same difference," Tom says dully.
"I will testify for you."
"I'd rather you didn't."
"Why not?"
Tom looks moody now, and rather condescendingly, as though speaking to a dim-witted child, he says, "If you testify for me they won't be able to administer the Dementor's Kiss. But they won't let me go either. So they'll give me the next best - or worst, depending on who you ask - thing: Life in Azkaban. I'd rather die."
Harry feels a headache mounting. It alarms him how involved he's become with the fate of the boy before him. He wishes he didn't care, but he does. To the point where he doesn't think he could live with himself if Tom Riddle spent an eternity in Azkaban, and all his youth and brilliance and - dare he say it - beauty wasted away. But what's the alternative? Set him loose into the world and risk everyone else dying? It's a moral conundrum, the first Harry has encountered in a world of black and whites.
"I should go," Harry says, gathering his things.
Tom's expression softens, and he reaches for Harry's arm before Harry can rise. "No don't," he says, gripping tightly, "Stay till sunrise."
So Harry stays. He settles back against the wall and hugs his knees, and they talk. This time about less depressing subjects- what Harry's going to do after the summer (go back to Hogwarts), and what comes after that (try to become an Auror?)
"I wish I could go to Hogwarts after the summer," Tom says sadly. "Voldemort really liked that place. I think what he felt for Hogwarts was as close as he ever came to loving anything."
"It was home," Harry says simply.
"And he'd never had one before Hogwarts," Tom agrees. "Nor did he ever have one after. He was always on the run after Hogwarts."
A silence, and then Tom begins again. "It's the small things I want most of all to have again."
"You miss them more than world domination?"
A smile tugs at the corners of Tom's lips. "I do, actually. I miss magic. There's nothing like the thrill of magic coursing through your veins and out of your wand. Even when you cast something as mundane as an Alohomora, say. I'd give anything to cast an Alohomora again."
"You make magic sound almost sexual."
Tom's laughter is a surprisingly happy sound, not the high pitched cackle Harry remembers from his worst nightmares. "You disagree?" Tom says. "Voldemort found it intensely sexual. He got off on dark magic."
"Why am I not surprised," Harry says wryly.
"He did get off like a normal human too, though. He and Bellatrix went at it like rabbits. Nagini was often involved."
Harry's lungs are thankful he's not drinking anything right now, because he goes into a severe coughing fit.
"There was a lot of sex in his last days," Tom continues helpfully. "I think he had to find some outlet for his frustration at not being able to get to you."
"Stop… talking…" Harry wheezes in between coughs. And then they both burst out laughing and Harry shudders even as he laughs, because the thought of Voldemort having an orgasm is as revolting as it is hilarious, and Tom laughs even harder, and then he stops and says "Shhh"
Harry turns to the door in panic, expecting Hagrid to barge in any second. "There's no one. It's just the birds," Tom says, sitting up and hugging his knees.
The birds are waking up in the trees.
Soon the sun wakes up too, and everything in its light is pink and tender. The mist through the attic window. The silent attic. Harry's invisibility cloak, glimmering by the door. The Weasley children's old toys and robes, lying mostly broken and torn in cardboard boxes stacked up to the ceiling. Tom's face, always turned towards the light.
Harry lets the silence of the early morning stretch on for as long as he can. He's surprised to find himself reluctant to leave, but the light is growing stronger every moment and he knows he must. He gathers his things, gets to his feet.
"Come again tomorrow, Harry?" Tom asks.
"See you," Harry whispers, and slips on the invisibility cloak.
Harry comes again the next day, and the next, and the next... The Weasleys worry about him because he sleeps all day, only appearing downstairs well after lunch, rubbing sleep from his eyes, but they don't suspect anything about his night-time activities. For a week, Harry keeps this up, returning night after night first out of sympathy for the cooped up and lonely ex-Dark Lord, then because he finds that he enjoys the other man's company. He likes that Tom thinks differently from anyone he's ever met, he likes Tom.
They talk about everything under the sun - the house system (to Harry's surprise Tom thinks it should be scrapped, he says it's too divisive. "You'd get rid of Slytherin?" Harry asks, and Tom nods. "I'm surprised it hasn't been done already. It's not a good idea to surround dark wizards in the making with other dark wizards in the making.. They only encourage each other."), the Ministry (Tom thinks the Ministry should do more to fund magical research, and the building of magical communities. "Magic has been stagnant for years and years, since wizards have had to go into hiding... We feel like we have to hide ourselves, so we can't do anything great, anything that would be too conspicuous. It's embarrassing - even the Muggles have advanced by leaps and bounds, and what do we have to show for ourselves?"), and smaller, simpler things, like their favourite parts of Hogwarts (Harry's is the sky above the lake, where he can fly without a care in the world. Tom's is the astronomy tower, where he used to sit late at night a very, very long time ago and work in the light of the stars), what it was like to grow up among muggles, their first kisses, the music they like... Slowly the attic transforms from a prison into a place of memory and reflection.
One night, Harry produces a gramophone from his satchel, and alongside it a record he'd found at Diagon Alley.
"Charles Mingus!" exclaims Tom with delight as the first notes begin to ripple, warm and quick and vibrant, across the attic. His delight is infectious; Harry finds himself smiling, tapping his feet to the fluid rhythm of the jazz without quite meaning to.
"Kiss me, Harry," Tom says out of the blue.
Harry doesn't know what to say.
"I know it's a strange request, but I'd like it if you humoured me."
"But we can't, Tom..."
"Bind my hands if you must." Tom turns and looks him in the eye. There's a voice in Harry's head that sounds just like Hermione and it's warning him how bad of an idea this is, warning him that he's getting played, but the other boy's gaze is so arresting that all the voices in Harry's head are drowned out, leaving just the saxophone's scream and a voice that simply says I want, and somehow Harry decides words are useless and thinking is confusing, and he simply lets I want guide him onto his knees. He's sure Tom can detect he's shaking ever so slightly, but the other boy makes no comment when Harry's trembling hands close around his wrists; he only leans in.
At first they're clumsy. Harry's never kissed a boy before, and he's not sure if this one will bite, so he kisses tentatively. And then he finds he likes the sandpaper roughness of a week's unchecked growth of stubble against his face, he likes the warmth and the roughness of kissing another boy and wishes he'd discovered it earlier, so when Tom's tongue probes against his mouth he lets it in, draws it deeper in until Tom moans and his wrists go weak in Harry's clasped hands. At some point Harry comes up for air. Tom is watching him hungrily. There's a feverish glow in his cheeks, or maybe it's just the sunrise.
Harry tells himself he really should be going before this gets out of control. But Tom is impossibly close and studying every minuscule movement he makes, and… Okay just once more then…
This time he takes his wand out of his back pocket and clutches it as they kiss, aware of the absurdity of the situation but not caring as Tom's free hands rove eagerly around his body, cupping his face, stroking his chest, coming to rest briefly around his waist. Charlie Mingus sounds his last note, and silence resumes in the attic but they barely notice. Harry grips his wand so tightly that golden sparks fly, stinging Tom in the neck, and Tom hisses but Harry can feel his mouth curve into a grin against his own, and Tom reaches down, down, down, finds the buckle in Harry's pants and deftly undoes it…
Harry pulls away, alarmed by how badly he wants what could come next and how much he's willing to risk to let it happen.
"I really should go," he says hastily, scrambling to his feet. Giving himself no time to change his mind, he puts as much distance as he can between him and Tom, willing his hard-on to subside. It doesn't.
Tom's expression is unreadable, but Harry can see him hunched over and panting slightly, like a wild animal in the middle of a hunt. "Accio satchel," Harry says, and this time Tom responds with a smirk that Harry does his best to ignore. He grabs his bag, the gramophone and the Mingus record, undoes the silencing spells and picks up the invisibility cloak.
"Well," he says awkwardly, dithering by the doorway.
"Well," Tom says.
"I guess I'll see you tomorrow."
Harry reaches Shell Cottage without any further incident. Thankfully everyone but the birds is still asleep when he climbs into bed. Mrs Weasley is the first to rise about an hour later, and Harry listens to the singing of her kettle, the clattering of her pots. Then Mr Weasley and Percy wake up, eat their breakfast quickly and apparate to the Ministry, then hours later, when the sunlight is bright and strong, it's everyone else's turn. Harry lies awake through all of this. Sleep does not come.