So, yes, I'm crossovering ( not a word*shut up ) the movie and the TV show, because I absolutely need a backstory for John Reese in Person of Interest. If you haven't read any one my crossover OSs on the matter, you still can ( if you don't mind knowing the end of the story before I finish writing this, that is ).

So, technically, John Reese is in this story, only he's not John Reese yet. He's John Sullivan ( movie ), Frank Sullivan ( TV show ) 's brother, and Raimy Sullivan ( TV show) 's uncle.

Oh, and no time-travelling radio.

Chapter 1: Nightingale

Roger smacked his back with too much energy, like always, and John winced.

"Well, Sullivan, I must say I'm still not sure how you did it, but congratulations! Homicide detective after only three years on the streets, I'm not sure I've ever heard of this before."

John eyed his partner – former partner, now, that he had been promoted – warily, waiting for the inevitable joke.

He wasn't disappointed – though he'd have rather been.

"You probably slept with the captain or something. Look at you, Sweetheart, twenty-four years old and cute as a movie star!"

Before John could protest, someone smacked Roger over the head.

"Thank you very much, Old Guy, I just needed that image in my head: my brother making out with Nelson O'Neil to get promoted. Dream of my life, really."

Frank, John's non-identical twin brother – and, really, they didn't look anything like the other, except they both had good looks – was standing behind the uniformed, older cop. He had just arrived to the small party Roger had insisted on throwing for John's promotion, because John wouldn't do it himself. Julia, Frank's wife, and Raimy, their four years old daughter, greeted "Uncle John" with big smiles.

Once John was liberated from his niece's arms, Roger turned back to Frank, and continued on.

"Well you can speak, Detective Frank Sullivan, but I do think there's something dubious in how the two of you brothers have been promoted with only two months in between. You, to Narcotics, and now John, to Homicides? I mean, come on, I get it for you, you're clever and you've been a cop for six years already, but your brother?"

John watched as Roger's daughter, Erin, went to play with – take care of, at this point – Raimy. The girl was older than his niece by a couple of years, but she seemed to know what to do to keep the younger kid's attention.

Drily, he addressed his partner's choice of words.

"What, I'm not clever enough, perhaps?"

Anton Roger was older than them all, at the end of his forties. Still a uniformed cop, too, but mostly because he didn't seem that interested in becoming a detective. He liked better to take care of the rookies like John, until they moved on to become detectives themselves, or they ended up taking care of the newest rookies themselves. Roger himself had had five different rookies under his wing, in all his NYPD career. John was the latest – and soon enough, there would be someone else.

"I didn't say that, kiddo! God knows you're more intelligent than I am, in a practical, get-shit-done way, most of the time. But unlike your brother, you only have three years in uniform under your belt, and that's probably the shortest time I ever saw someone do before getting promoted to detective. Homicide detective, at that."

John snorted.

"Right. Well, while you're imagining things about me and the captain, I'm going to get a drink."

The truth was John had an uncanny ability to detect a liar – especially a man – and he could literally tell you whether or not someone'd be able to commit a cold-blooded murder just by observing them for a while. It's wasn't quite finding out who did it with a single glance, but it was damn helpful. Over the three years he had spent doing patrols with Roger and being called onto crime scenes to take the first witnesses statements, he had often implied some of his deductions to the detective handling the case, and most of the time, he had turned out to be right.

Not always, but often enough for it to be noticeable, for someone higher up to consider him fit to become a detective.

Something John had waited for a long time, now. It was always easier to investigate as a detective than as a uniformed cop. People simply didn't react the same way.

He had a killer to catch, and he had already waited eleven years to be able to do it properly.

Standing at the table, serving himself a glass of wine, John glanced at the few people Roger had invited for his little promotion party.

There was, of course, Roger and his wife. Things were getting strained there, even if they still managed to laugh together, and John wasn't certain it would hold much longer between them, but he hoped he was wrong; for Roger, of course, but also for Erin.

Then, there was Frank, Julia and Raimy. The only family he had left. Frank's and John's father had been in the military when they had been born, and had stayed there for yet six years after their birth. Then, in 1974, Conor Sullivan had come home to Puyallup, Washington, and stayed there; he had become a firefighter, and had died two years later saving four people from a raging fire. Margaret Sullivan and the twins had moved to New York, and started a new life there. But Margaret was a nurse, and when the Nightingale Killer started his serial murders, she became the third victim.

That had been eleven years ago, in 1981. John and Frank had only been thirteen when they had become orphans.

Maria Graso should have been there too, at this party, but John's and Frank's foster mother had died in a car accident in 1985. They had been sent into a few other foster homes, but soon enough, John had disappeared, had left. Frank had completed his studies, and joined the NYPD, without ever getting any news from his brother.

In 1988, John had come back, apologized, and refused to explain where he had been all this time. Frank still thought he had been travelling through the USA, perhaps committing a few minor errors, but nothing grave, and certainly nothing that any law enforcement knew about.

John had joined the NYPD almost as soon as he had gotten back in New York, only finishing his studies beforehand – easy enough, considering he was far from stupid, even if he sometimes made terrible decisions.

And here he was, now, standing in his partner's living room, his family and a couple of colleagues present too, joking around and wishing him luck as a newly promoted detective for the 21st precinct.

They had no idea of what he was planning to do now that he wasn't out patrolling anymore, of course. John was very good at putting a fake smile on his face whenever needed, and even better at not mentioning some things about himself.

Even Frank didn't know for sure that John was going to go after the Nightingale Killer.

Oh, his brother probably had an inkling, if nothing else. They were, after all, twins, and Frank himself had tried to look at the case since he had become a detective, two months before. But Frank wasn't overly obsessed with it, either – he'd like for the killings to stop, for the killer to be caught, for their mother's murderer to be punished, but he wasn't like John.

John would do his job, like any other detective, but all he really cared about for now was to get the bastard who had taken their last remaining parent away. It wasn't really a matter of killing him or not, it was about avenging their mom. It was about getting definite closure... And since, even after eleven years, the serial killer was still making one victim every three months or so, John needed to be part of those who'd take him down. The detectives on the case still had very little clues as to who the man was...

Even after all this time.

John couldn't not take part.

Besides, should things go that way, he didn't really mind killing the bastard – and he wasn't just thinking it, like any vengeful son would; he knew it to be true. He had killed before, and this time, unlike the preceding time, the man deserved it.

If he couldn't get the Nightingale Killer arrested... Then he'd kill him. He'd find a way to make it legit. It wouldn't be too hard, really, considering the number of victims. If the evidence was too circumstancial, or completely missing, if there was the slightest chance the bastard would walk away... John'd follow him as long as needed, even if he had to get him literally red-handed. He'd make his life hell.

Because no matter what, he was going to find the Nightingale Killer.

What he'd do after that... Well. That was still to be considered.

He'd have to see how revenge sat with him, before deciding anything. He'd have to experience the feeling, to see if it'd change something in him, or not.

Because if there was one thing John knew about himself, it was that his ease with busting out killers and other liars came from his own capacities at both activities. He had no interest being a criminal, and didn't intend to become one, but shall the need arise... He'd do anything to protect those who had to be protected. Even if it meant covering his hands in blood. Even if it meant lying to Frank.

John went back to the laughing group, a small, unassuming smile on his lips. Not exactly shy, but a little embarrassed by the attention – it wasn't even a lie, he was uncomfortable with the congratulations and everything else. Only, in the end, it wasn't what mattered more here.

They stayed about three hours at the Rogers', and John even witnessed Erin Roger giving a customized lighter to her father with a big, innocent smile.

He wondered if, one day, he'd have a family, just like his partner. For now, he was too focused on his quarry, but once that'd be dealt with, perhaps... One or two kids, boys, girls, he didn't really care eitherway, and a mother for them. A wife. Someone new in his life, someone he didn't have right now. A larger family. Cousins for Raimy.

Later.

When Roger's wife sent Erin to sleep, Julia decided it was time for Raimy to go home too. Frank kissed his daughter on the forehead, told them he was accompanying John home, and then he'd be home too.

John gave his brother an odd look as they left the Rogers'.

"What, you're not trusting me to go back to my place if I'm left alone? I'm not much of a party animal, you know, and I'm certainly not going to drink myself into unconsciousness the day before my first shift as a detective."

Frank snorted.

"Your place is far away enough, and your partner drove you here."

The taller of the two Sullivan brothers continued eyeing the other dubiously.

"I won't get attacked in an alley, if that's what you're worried about."

Frank didn't answer that, but the look in his eyes said enough: whoever might be stupid enough to try and mug John Sullivan had better be heavily armed, or not alone, because John had proved more than once that he kicked ass whenever someone thought they could get away with manhandling either John, Frank, or someone else entirely.

In high school, John had been the official bully-proof terror.

Frank still angled his jacket better, so that the police badge would be visible to anyone who thought they could try something. His gun wasn't visible, but still there.

John'd know, he did the exact same thing everyday.

Sometimes, it was better to just warn off the possible attackers.

"We need to talk."

God. The sentence. The one no one ever wanted to hear in any kind of relationship – romantic, familial, employer and employee...

Still, despite his earlier words, Frank didn't speak right away. They walked in silence for about ten minutes before he said anything. And even then, John had a feeling this wasn't what his brother had first wanted to say. That would come up, surely, but later.

"Do you know if you have been assigned a partner yet?"

John shrugged. The 21st precinct didn't have a free detective to pair up with him, it seemed, because one of them was on sick leave. Ellie Goff had caught whatever illness her son had brought back from school, and so her partner was being paired up with the other lonely detective whose own partner had been transferred to the 51st, leaving a spot for John.

"Not sure yet. The logical choice would be Harper, but with Goff on leave... I guess I'll have to wait until she comes back."

"Be careful, then. Not having an official partner doesn't exactly mean you don't have any back-up, but still..."

John actually liked it better. That way, at least, he would be able to start his investigation about the Nightingale Killer discreetly, without having to worry that his not-there-yet partner might be wondering what he was doing.

Of course, he'd have to deal with keeping it a secret from his partner at some point, because Goff wasn't going to be absent forever, but if he could at least get it all on track before that happened...

"I can defend myself, Frank."

They were standing in front of John's building, but neither of them were making a move to leave nor go inside, yet. John could tell his brother had more to say, and he also knew that Frank wouldn't be fooled if he pretended not to have noticed.

"Oh, believe me, John, I know. In fact, I noticed you've gotten even better at hand-to-hand combat, since high school. These few moves Dad taught us? You've completed them, as if the rest of your fighting skills just upgraded to fit with them. I've seen you handling that guy, three weeks ago. You and Vasquez, you fought in sync against him."

John gave his brother a cool – not threatening, of course, but utterly disinterested, yes – look.

"Your point?"

"Vasquez used to be a soldier, John. And you were perfectly in sync. Most of the time, you go on using simpler moves, but because that time it was more efficient to play along Vasquez's tune, you adapted, and you knew how to. Now, I don't know where you were these three missing years, what you were doing, but it's obvious someone taught you how to fight above the usual punch to the face. There are a number of plausible reasons for that, and most are not a problem, but some are. So tell me, please, that you don't have dark secrets waiting to jump at your throat the moment you don't expect it."

John smiled slighty, as he always did whenever his brother got worried over him.

Well, with a detective for a brother, it wasn't exactly surprising that Frank would figure out some things. The point, now, was whether or not John'd be able to control the deductions his brother would make out of his observations.

Because as long as Frank didn't exactly know what he was hiding, as long as he thought John was keeping things to himself because of some particular reason and not because of another kind of reasons... There wouldn't be a problem.

All John had to do was to let Frank think he had found out enough, that nothing harmful could come out of it, but that he just didn't want to talk about it...

"I don't have dark secrets waiting to jump at my throat the moment I don't expect it."

Truthfully, John always expected one of his secrets to jump at his throat.

"I swear, Frank. The people I met while I was away... I won't say they were all perfectly upstanding citizens, mostly because I didn't know any of them enough to be sure of such a thing. But they were trying to do good, if anything. Whatever their reasons. And, well, some of them were marines. They taught me a few things along the way."

Technically true. Most of the people John had been acquainted to in the three years he had spent away from New York were marines, and they had taught him how to fight like a marine. Since, you know, he had enlisted to be one.

Frank didn't know about that last part, and John intended to keep it this way.

Lying by omission really wasn't a thing for him. You can't lie if you don't say anything. You omit some things, true, but it's not a lie. It's an omission.

If it wasn't, then everybody would always be lying, simply because you don't tell absolutely everything about yourself and what you do in the WC to everyone you meet. Some things always went unsaid, be it because you simply hadn't thought about it, or because you decides not to speak of it. Whether the omission was voluntary or not was another question altogether.

Frank wasn't completely convinced, but he wouldn't push – for now.

"If you say so... Well. Stay safe, John."

"Stay safe, Frank."

And just like that, the brothers parted ways. Frank went back to his family, and John walked up to his small apartment. Alone.

In his bedroom, John put down his gun, his badge, and turned back to stare at the blank wall in front of his bed. There was absolutely nothing on it, not even a fake painting, but he intended to change that soon. He already had one thing to put on that wall, and before the end of the next day, there would be more.

John pinned a picture of Margaret Sullivan in the middle of the white wall.

One day he'd add a picture of the Nightingale Killer, he'd make sure of that.