Lab. I swear, all anyone has to do to write Sherlock fanfiction is to make obscure deductions during their chemistry lab period and then go home to write. In the previous one-shot (She's A Graduate Chemist) I failed to mention that the Wrightlock ship is going to be fuelling several more one-shots, each with their own prompt…chemical, I suppose, even if that chemical isn't necessarily a part of the story. It'll just be one I was working with on the day I wrote it. The last chemical prompt was acetone, or C3-H6-O. Today, the chemical prompt is acetaminophen, or C8-H9-NO2.

Oneshot Summary: Mary plays baby-sitter to Sherlock, Sherlock plays nursemaid to baby Daisy, and Susan brings food. John's on call at the ER. Poor John.


Mary Watson was inwardly cursing her husband for deciding it was a good idea to leave Sherlock with her while he was at work. While she thoroughly agreed it was best that Sherlock wasn't left to his own devices, she didn't see why she was the only available candidate suitable to watch him. Mycroft could keep a rein on his little brother, and Sherlock was dying to get back to the morgue now that Molly had more free time. It wasn't quite fair, she thought, that she was suddenly the most fitting out of the lot just because baby Margaret—Daisy, for short—had changed her temperament to such a degree that she wouldn't do more than scold Sherlock if he did something…Sherlockish.

Not that anything had gone wrong, of course. The moment that Sherlock had stepped into her flat, he had ordered her onto the sofa to rest, cleaned the cluttered living room (which both Mary and John were far, far too tired to look after now) and made her a cup of tea. When Daisy had awoken an hour later, he had fetched her from upstairs so Mary could feed her and rock her back to sleep again. No, Mary was fuming because she felt terrible about letting Sherlock do all the work that she and her husband had been neglecting for the past two weeks. Three hours after Sherlock had arrived, the four tiny rooms of the flat had been thoroughly tidied, the stove had been scrubbed, Daisy had been bathed (Mary could never calm her during her bath as well as Sherlock just had) , two loads of laundry had been finished, and her ramshackle kitchen cupboards were organized. It wasn't the system she'd have chosen, but she could see all the dishes and pick out the ones she wanted right away.

But she couldn't keep from smiling every time Sherlock held his new god-daughter in his arms. Daisy never cried with him, and even seemed to be essaying a smile for all she was worth when he sang her lullabies. Daisy wasn't quite there yet, but she was trying. She was only a month old, after all. So although she was horribly guilty, Sherlock and Daisy seemed to be in their element—and it was so nice to see the house looking clean again after so many weeks of it looking so dreadful. At the moment, Sherlock was sitting in the nursery, reading Daisy a book he had brought about the elements.

"It's never too soon to learn, Mary," he said haughtily, after catching a glimpse of her raised eyebrows. "She's an intelligent baby, and with any luck she'll develop excellent deduction of her own."

Mary sighed in contentment. Yes, all was as it should be. John had been called in to the emergency shift at the local hospital, and he would be home soon. It was at that moment that the telephone rang.

"Mary?" said the musical voice from the other end of the line. "I made a lasagna for dinner—I'm having some of my colleagues over. I made extra, though, so would you like some?"

"Susan!" said Mary in delight. "How've you been? I haven't seen you since—"

"Since before Margaret was born, I know," laughed Susan. "But I'm driving near your neighborhood anyway in a few hours, so I thought I might drop off some food. I know you love lasagna."

"Come, and be prepared to stay for a while," Mary replied. "Sherlock's here and he insisted on cleaning the house, so I'll actually be able to start inviting people in again. I'm sure he'd like to see you as well. And Margaret! You can't go until you've seen her, too."

"I'd love to," said Susan. Mary smiled—Susan's voice sounded slightly shy, and it definitely wasn't because she would finally get to see the baby. "I'll be over in half an hour or so, is that all right?"

"Of course. I'll see you then."

As soon as Mary hung up the phone, she parted her lips to call Sherlock and tell him that Susan would be coming over with lasagna, but she closed them just as quickly.

Susan's arrival should be a surprise.

"She doesn't seem to want to sleep." Sherlock strode into the room fifteen minutes later with Daisy nestled on his shoulder. Her brown eyes were wide open, and she was looking around the room as if every object in it caught her interest. "An observant child already, Mary."

"Give her here," smiled Mary, holding up her arms for her little girl and kissing her as soon as Sherlock handed her over. "She's beautiful, isn't she, Sherlock?"

"She is in perfect health, and she possesses no lack of the evolutionary wiles babies use to enchant people into looking after them," said Sherlock dryly. "But she is strong, well-behaved, and already appears to have an acute intellect despite the fact that she's only five weeks old."

"Oh, shut it," Mary swatted his shoulder. "You know perfectly well that's not what I meant."

Sherlock smirked. "Maybe."

He ambled off into the study—probably to ransack John's books and read up some strange facts about small children.

Within five minutes, the doorbell tinkled. Mary opened the door and hugged Susan, almost upsetting the covered dish her friend was holding in the process.

"I missed you, too," said the amused Susan.

The moment she spoke, Sherlock shot straight out of the study and back into the living room.

"Susan," he said, seeming to remember the enlightening evening they had had at the fish and chips restaurant on Baker Street.

"Sherlock," she said, favoring him with a smile. She took a deep breath and glanced around the flat. "It's so homelike here. I had a horrible headache earlier, but it felt like I'd taken a paracetamol when I walked in. It doesn't hurt nearly "

"Acetaminophen," said Sherlock quietly. "I usually prefer to call painkillers by the names of their active ingredient or ingredients."

"What do you do if there are many?" asked Susan. "Do you just list them all and hope the drugstore clerk will know what you mean?" She shot a grin at Mary behind Sherlock's back and then turned back to him, a questioning look on her face.

"I usually refrain from purchasing those particular ones, if it's an over-the-counter order," said Sherlock long-sufferingly. "I used to try to persuade them to learn the correct names, but none of them have ever listened to me."

"How dare they," she quipped. Sherlock cracked a tiny smile and stooped to the cradle beside the sofa, lifting Daisy out with almost breathless care. Susan felt her own hearbeat speed up as she drew nearer to him, gazing at the baby he held.

"Mary—Mary's she's absolutely perfect," she breathed, her arms reaching forward almost of her own accord. Catching herself, she turned back to her friend. "Can I?"

"Of course," said Mary. Sherlock extended his arms and placed the child into Susan's.

It took a moment for her to adjust to the weight of the little girl—not because she was heavy, she was incredibly light—but because holding her placed a pressure on her heart that made her want to laugh and cry at once.

"Feel it, don't you?" asked Mary, looking knowingly at her friend.

"Yes," Susan almost gasped. "Oh, Mary, she's lovely. Look at her eyes! I thought babies weren't able to focus this well at a month old."

"She certainly is exceptional," Sherlock agreed.

"I used to wonder how women could go from agony while having their babies to bliss two minutes later," said Susan in wonder, handing Daisy back to Mary. "I always thought I'd need a bit more of a recovery stretch, if it were me. But she's completely cured my headache. A second round of the paracemamol effect," she said with a grin.

"Acetaminophen," said Sherlock from his spot on the sofa. Susan rolled her eyes.