Sherlock spent the night after John begged him not to leave him alone in his predicament. When the consulting detective woke up the following morning after a particularly uncomfortable night's sleep on John and Mary's sofa, he stumbled into the kitchen to find John seated in front of a table, the mystery baby seated in his lap and a laptop out in front of him.
"You put him in a dress," Sherlock commented, coming up to the other man from behind.
John didn't look up from what he was doing online. "All we have are dresses. Mary can't seem to stop buying her dresses. Thankfully these fit."
"Hm." Sherlock leaned further over the doctor's shoulder, trying to get a better look at his laptop screen. He squinted. "Is that a mum's forum?"
Leaning back in his seat, John turned his head just enough to glare back at the detective. "It's the email thread from our Mummy and Me class," he told the other man rather matter-of-factly. "They're fairly up to date with the ongoings of the early parenting community. I figured if anyone ought to know of something like this happening, they would."
"You go to a Mummy and Me class?" Sherlock asked skeptically.
John let out an exasperated sigh. "That's just a part of the title. Parental-infant bonding isn't limited to one sex. For instance, there's this one same-sex couple there, Paul and Henry - I'm sure you'd like them. They're really nice."
"I bet," smirked Sherlock.
"Oh God not like that!"
"Are you the only other father in the group?"
John pursed his lips together thoughtfully and stared forward. "Although that would explain why they're always so eager to invite us over for playdates," he said softly.
A silence filled the room and John went back to his computer screen. Sherlock turned away with disinterest and began digging around through the cupboards. After a couple moments of this he found a box of cereal, which he began to eat straight out of the box, his back leaning against the kitchen counter now.
"So does this Mummy and Me class know all about your little ordeal?" the man finally asked between fistfuls of the dry cereal.
"I'm not stupid, you know," John muttered. "If I were to admit to this any one of them would have Mary on the phone in a matter of seconds, and then she'd be on a plane back here by tonight and I'd never hear to end of it!" John turned around in his seat to face Sherlock now. "And that's assuming she wouldn't want a divorce right away. Can you imagine? She'd be furious! Never trust me with my own daughter again!"
"Or son."
"What?"
Sherlock smiled. "Assuming we never make the switch back."
John let out a low growl, but before he could respond a little bell sound trilled from his laptop speakers. John turned back to face the screen and his face fell. "Oh no."
"What is it?" Sherlock asked. But he only had to look up and see an enlarged picture of Mary smiling back at him across the screen to know.
"Mary wants to video chat," John told him. He seemed to go pale as he said this.
"Ignore it?" Sherlock suggested with a shrug.
"I can't," John whined. "Too suspicious. Here, take him." The man got up and shoved the baby into Sherlock's arms. Sherlock accepted the child but opened his mouth to protest. John, however, didn't let allow him time to do so and instead shooed the detective out of the room. Once Sherlock was out of sight John scurried back over to his computer and accepted the call, lounging back in his chair hopes of looking as inconspicuous as possible. "Mary! Hey!" he grinned. "How's, um… the uh…"
"Graduation?" his wife asked through the computer's speakers.
"Yes! Exactly! How was it?" John asked, trying his best to keep from looking guilty.
"It was alright," Mary told him. "Cap and gowns. No one tripped picking up their diplomas. Lots of singing and tears. How are you holding up? Getting any sleep?"
John rubbed at an eye and smiled back. "No. But that's life."
"Can I see her?" Mary asked softly.
"Um… Actually, she's still sleeping. Looked dead tired after staying up all night crying."
"Oh, she misses her mummy," cooed Mary lovingly. "Can you at least take the camera over to her? I'd still like to see her. It's been lonely without my two favorite people in the whole world."
"Actually, um, I-I uh, I have a… a thing, and um-"
"Oh, Mary, hello!" Sherlock let out in an almost uncharacteristically cheery tone as he peered out from over John's shoulder.
"Sherlock! What a pleasant surprise."
John gestured to his friend. "Ah, yes. Um. Sherlock. H-He, uh… That's the thing. That I have. He is the... thing. Yes"
"Case?" Mary asked.
"Always. Speaking of, John and I are kind of in a hurry. We already called a sitter so you don't need to worry about anything else, Mrs. Watson. Cheerio!"
Before John or Mary even had a chance to say goodbye to one another, Sherlock slammed the laptop shut and took a couple steps away from it.
"Great!" John criticized. "Now Mary's definitely going to know something's up!"
"Oh, relax," Sherlock let out, holding up a dismissive hand.
"Where is he?"
"Who?"
"The baby. Where is he? What have you done with him?"
"Oh. Nothing. I… set him down on the sofa," shrugged Sherlock.
John's eyes widened. "Y-You what?!" Suddenly the man was on his feet sprinting towards the other room, all the while shouting "Sherlock! He's an infant for Christ's sakes! What if he falls over and hurts his head or something? We'd be personally responsible for any developmental-" The doctor stopped suddenly, seeing that the stranger's baby was not on the sofa, but lying down in his daughter's crib.
"I'm not entirely clueless when it comes to caring for small children," Sherlock said, coming up beside John. "You, on the other hand, are completely sleep deprived and paranoid."