A/N: I had written this before realizing how wrong the biology was. I'm not going to fix it, but I hope you guys enjoy the fic regardless.
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It was a rarity when John had the flat all to himself. He told the truth to Mycroft: he was never bored with Sherlock. But that man took so much energy to be around, John often went to bed exhausted in both body and spirit.
Today was a rare empty day, in which Sherlock was off at the morgue either returning the corpse parts he had or obtaining more- John wasn't sure. The flat was empty and John was going to use that to his advantage by occupying the couch as much as he could and sleeping the day away.
And then the front door knocked.
John sighed slightly, checked the time- it had only been two hours of blissful peace- and got up to answer the door. He thought it might be Mrs. Hudson, as Sherlock never knocks, even when John was in the shower or getting dressed in his room.
John got up, stretched his limbs and feeling good about it. So lazy, he thought warmly as he padded his way to the door. He opened it, and the world suddenly came to a complete halt.
John will never be as good as Sherlock, but he was learning. Sometimes when he was on his own, John would try to deduce the random stranger by looking at their rings, shoes, or hair. When coming into a new environment, he will determine the space, the exits, and the direction of the sun streaming in from the windows.
So as soon as he opened that door, his first thoughts were, How did he get past the CCTV cameras? Disabled? No, otherwise Mycroft would already be here. He found a way around them, to fool them.
The baby in Moriarty's hands however… that was harder to deduce.
"Afternoon, Johnny," Moriarty smiled. The baby he held in his arms turned his head to look at John, and he only got a glimpse of bright blue eyes before it turned around again, burying his face in Moriarty's neck. "May we come in?"
John's lips tightened, glancing down at the babe before stepping aside to let them in.
Moriarty had a diaper bag with him- the fuckin' psychopath brought a fuckin' diaper bag with him!- and he placed it down on the coffee table before settling down on the couch. He readjusted the baby so it sat on his lap. "This is Christian," Moriarty explained. "Isn't he beautiful?"
The baby certainly was. He had pale skin, pitch black hair and red lips, making John think of the Snow White fairy tale. He looked to be only seven months old and he wore a deep purple, one-piece outfit.
"Yes," John agreed, coming into the living room slowly. He tried to think of a way out of this, tried to think of a way to keep himself and that baby alive. He couldn't call for help, his mobile phone was in his room charging.
His back was sweating something fierce. If it was just him, just his life on the line, John would otherwise revel in the adrenaline pumping through his veins at the moment. Instead, he felt sick to his stomach.
"John," Moriarty tapped the cushion next to him. "Come sit with me."
There was no threat, no tone in Moriarty's voice indicating there was one. It made John angry, how confident the mad man was.
He looked briefly back at the door, never noticing until now how fuckin' far away it was. There was no way John could just grab Christian and run, not unless he can guarantee Moriarty did not have a gun or knife on his person.
He sat down. Moriarty passed Christian over to him.
John didn't know why Moriarty did that. He decided didn't care and immediately drew the baby closer to himself, protecting it. Christian squirmed at nearly being engulfed and when John didn't relent his hold, he started to wail.
"Don't hold my son so tightly," Moriarty scolded lightly.
"Your son," John hissed. He backed off slightly, giving Christian room to breathe. "You're telling me there's a woman out there who was willing to carry your off-spring?"
"My sister."
That was like a kick to the head. Unwillingly the thoughts of incest ran rampant in John's brain and he tried not to think any further than, His sister carried his baby.
Gross, gross, gross, gross, gross.
John tried not to show any outwardly disgust, not wanting to offend the incest-invoking psychopath sitting across him, but something must've shown on his face because Moriarty giggled lightly and said, "I am not the donor."
"Then that doesn't make him your son."
"My sister is a twin, John," he then reached up and plucked a lone hair from his head. He pulled out a white handkerchief and placed said hair in the folds. "Here, do all the tests you want. Either way, DNA will show he is mine."
"Still doesn't count."
"Aren't you curious about the donor?" He was positively giddy when he said that.
"Sherlock," John said automatically because who else would it be?
"No, silly," the grin on Moriarty's face was downright inhuman. "It's you."
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Christian was a quiet child. The only time he cried was when he needed something and the moment he got it, he stopped crying almost immediately.
Of course John thought about having kids one day. In the future, maybe, when he was confident he wasn't going to hurt someone because of his PTSD, when he found the right woman, had enough money, ect, ect. It wasn't confirmed yet Christian was his son but something deep in John's gut he knew the truth.
It was early in Harry's and Clara's marriage when they had asked John to be a donor. John had hesitated at first but when it was announced he was going to be shipped out to Afghanistan, he broke and froze a sample of his sperm should something ever happen to him.
He'd never told Harry or Clara what he had done, wanting the option of taking back the sperm when (if) he came back. Getting shot and meeting Sherlock shoved the whole incident to the back of his head.
"You don't have to keep him," Sherlock said to him. "You can just dump him in the nearest orphanage."
Not even Sherlock doubted Moriarty's words about Christian. And this disturbed John more than he thought it should. "If he was your son, would you leave him in an orphanage?"
"In a heartbeat."
John expected such an answer. It still didn't stop the disappointment he felt. Instead of saying that, he said, "We both know we cannot leave Christian in some orphanage. Son or not, Moriarty has singled out this child for some awful reason and I'm not about to let that kid suffer at his hands."
"Give him to Mycroft."
"Mycroft wants children?"
"Don't be an idiot," Sherlock huffed. "Mycroft will find the child a family, somewhere he can be safe."
His phone beeped. Sherlock glanced at the text message just for a second before showing John the screen.
TESTS CONFIRMED.
JOHN AND HAIR SAMPLE ARE THE BIOLOGICAL PARENTS.
-LESTRADE
John didn't know he was holding onto a shred of hope up to that point. Maybe Moriarty had been fucking with his head. Maybe Christian was Moriarty's son but not John's.
It didn't matter now. John let out a slow sigh and got to his feet. He kneeled down in front of Christian, picked him up and pulled him close. The babe gave a short little squirm. "I don't love you," John whispered to him. "Not yet. Give me time."