Normally, John was all for Sherlock letting Hamish watch his experiments. As long as Sherlock abided by the list of rules John had set. The list of rules that were written in red and stuck to the fridge.

He must not be allowed to touch anything harmful.

He must not be invited to 'hold this' under ANY CIRCUMSTANCES.

He must not be allowed to decide what gets added 'for extra fun'.

He must stay on the opposite side of the kitchen island at all times.

The following roles are NEVER ALLOWED:
- Acid chooser

- Substance shaker/stirrer/mixer

- Test subject

- NEVER TEST SUBJECT

- EVER

Never let him out of your sight (that goes for Hamish too)

Never show him where anything harmful is kept.

Disallow him to talk at great length (also applies for you, Sherlock)

It wasn't a drastically outlandish list. But Sherlock still saw fit to criticise John's views of him as a parent.

'Do you really think I could be so irresponsible, John? Really?"

To which John's reply was simply,

"Yes."

Sherlock had clenched his jaw and not spoken to John for a day after that. At first John had felt guilty, perhaps his list had been a bit offensive towards Sherlock. But it didn't mean the list was any less meaningful. Every single thing on it was capable of happening and every single thing on it John didn't want happening. Call him the Mother of the family, but it was true.

So naturally, especially after Sherlock had sworn blind that he was much more capable than John made him out to be, when John entered the flat one evening after a late shift at work to find Hamish in the kitchen, stood on a stool, his hand being held under the tap by Sherlock, the doctor wasn't impressed in the slightest.

"What the bloody hell has happened?" John asked, quickly dropping his keys onto the worktop and rounding the counter to reach them. Sherlock had the sleeves of his purple shirt rolled up to his elbows and a gentle hold on Hamish's right wrist, guiding his hand under the flow of water from the tap. The detective turned to John, his dark curls falling against his forehead, and smiled.

"Oh, nothing to worry about, John. Just a minor Bunsen burn. It's all being taken care of." Sherlock turned back to his son, avoiding the scowl from John that ended up hitting his back instead of his eyes.

"Sherlock. Please don't tell me you burned our son." John was seething, breathing through his teeth and trying hard to remain calm but his fists were clenching and unclenching.

Sherlock turned again to face John, still holding Hamish's wrist. "Okay." He paused before flashing a brief smile and turning back once again.

"Sherlock-"

"I'm fine, Dad! It's fine!" Hamish cut John off, trying to protect his father.

"See? He's fine." Sherlock whispered reassuringly and John grit his teeth, shifting his stance in annoyance.

"Let me have a look." John stepped over to them both and nudged Sherlock out of the way. He turned the tap off and grabbed Hamish's wrist gently to lift it into the light. "Where's the burn?" He asked after a moment's confusion.

John frowned at his son's perfectly-fine arm for a second before looking up at him in question. Hamish was grinning.

Sherlock's baritone laughter suddenly filled the small kitchen, soon joined by Hamish higher giggling. The boy took his wrist out of John's grasp so he could reach across and high-five his father.

John felt like shouting.

"See?" Sherlock was suddenly behind him. "I'm better at this parenting lark than you think, John." He bent his head to press an affectionate kiss to John's cheek and Hamish wrinkled his nose.

"Yuck." He shielded his eyes and John even let out a light laugh.

"Alright, Lord Laughs-A-Lot. Go and get changed for bed." The doctor pointed towards the door.

Hamish hopped down from the stool, still laughing, and bounded out of the room.

"You really don't have much faith in me, do you?" Sherlock asked after a moment's silence.

John turned to look at the dark-haired man and lifted a hand to cradle his face. "It's not that. It's just… I know what you're like when you get excited about something. You can get a bit… eccentric and… bouncy. And even though your deductions manage to stay as sharp as they ever are, your… decisions can become somewhat… stupid."

Sherlock pursed his lips with a frown. "Give me an example."

"Oh, I don't know – running out in front of a bus?" John exclaimed.

Sherlock face fell. "I see. And this makes you worry for the welfare of our son when he's in my care, is that it?"

John sighed and stroked his thumb across Sherlock's cheek. "Only a little bit. But I trust you. And if you say you can control your… eccentricity when looking after Hamish then… you can." John smiled and Sherlock returned it half-heartedly.

"Oi. Don't go sulky on me now, we were having a laugh a minute ago weren't we?"

Sherlock didn't answer, instead he bent his head to press a chaste kiss to John's lips.

"Ugh, I'll come back later." Hamish spoke from the doorway.

Both men turned to look at him and John frowned.

"Hey, I thought I told you to get ready for bed? Hmm?" He lightly scolded.

"Yeah, but I just came to ask Father a question first." Hamish replied and looked at Sherlock.

"Go on then, but quickly." John gave in with a sigh.

"When you said 'don't get anything in that cut', you know the one on my finger from the scalpel, does toothpaste count?" Hamish asked innocently and silence fell in the kitchen.

Sherlock's eyes widened and he could feel John's glare on him without having to turn and look.

"Err…yes. Toothpaste counts, Hamish." Sherlock replied awkwardly. "Just…go and get your pyjamas on and I'll come and help."

"No, you won't." John stopped the detective from walking towards the door and Sherlock smiled apologetically at Hamish.

Hamish noticed the tension between his fathers and thought it best to make himself scarce.

"Scalpel?" John asked.

"Well it was an accident, he leant across to point at something and-"

"Scalpel." John repeated but it was now a statement.

Sherlock stayed silent.

"You let our son near you, with a scalpel."

"Well he didn't have the scalpel. I did so-"

"That's bloody worse, Sherlock!"

The detective breathed in deeply and raised his chin. "If you're just going to curse, John. This conversation will get nowhere."

John shook his head and quirked a disbelieving smile. "You know, sometimes…sometimes you can just so easily…"

"Father?" Hamish called from his bedroom and Sherlock leapt at this opportunity.

"Yes, Hamish! Coming!" The detective darted out of the kitchen after flashing a grin at his husband.