Five years after the events of "The Six Thatchers":

"Mike…please tell me you're joking," John Watson intoned quietly to Mike Stamford as the two sat in Mike's consulting room, with five-year old Rosie sitting on the exam table between them, swinging her legs while she looked at a book.

The other doctor looked back at John, a pained expression on his face. "I'm sorry to say that it's true, John," he said. "Rosie's most recent labs have shown no improvement. I've asked for a consultation this week with Dr. Cooke, our finest nephrologist, but I think it's pretty clear—her kidneys have failed. I think Dr. Cooke will recommend dialysis, with a transplant if possible."

A cold hand gripped his heart as John slumped in his chair. "I was hoping…praying…that there would be some turnaround. But ever since the HUS she developed last year after that infection, I had a nasty feeling something like this would happen. Fits our typical luck."

"I understand," said Mike, nodding slowly. "I'm sorry, John."

"It's all right, Mike," John said with a faint smile, trying to reassure his old classmate. "You've done everything you could."

He and Rosie walked out of the hospital hand-in-hand and made their way up the street toward the bus stop. The afternoon sunlight glinted off his daughter's blond curls, and he could swear his Mary looked back at him from her face as she turned to look up at him.

"Daddy," she asked, "What did Uncle Mike mean when he said, 'die…dielsis'?"

It was all he could do to keep from crying. She didn't deserve this. He guided her to a bench near the stop and they sat. "Sweetheart," he said gently, "You have a part inside you, two of them, really, called kidneys. You remember that time last fall when you got sick?"

She nodded seriously.

"Well, when that happened, something happened to make your kidneys sick, too, and they've stopped working. So…dialysis is something that we have to do to help keep you from getting sicker. And if we're really lucky, you might be able to get a new kidney, and then you wouldn't have to do dialysis anymore, yeah?"

"I could get a new one?" she asked incredulously.

"Yes," he answered. "But it has to be a special one, and it might take a while to find the right one for you. You can bet that I'll be tested straight away to see if I can give you one of mine."

"But then you'd only have one!" she protested.

He ruffled her hair. "I'd gladly give you both of mine if it meant you were well again," he said.

Rosie smiled and put her little arms around his waist. "Thank you, Daddy," she chirped.

John put his arm around her, holding her close to him. Their family was small, just the two of them now, and he didn't know what he would do if something happened to this precious child. He swore inwardly he would do whatever it took to keep her healthy. As he squeezed her tightly, his eyes fell onto a section of the pavement near their bench, and he suddenly realized where they were, outside the old pathology department at Bart's, and unwanted memories intruded into his thoughts…people crowded around a figure on the ground, dark blood pooling from the head…and he, John Watson, struggling to get through…let me through…he's my friend…lifeless eyes and…no. No, he wouldn't go there again. It was all too painful, painful the first time and still painful now, all those years later. He hadn't been in contact with Sherlock since… he closed his eyes tightly…since Mary died. The detective had tried a few times, but John had been adamant, and finally, Sherlock had just disappeared. Once in a while, John would see a mention of him in the paper or on the telly news, but they hadn't spoken otherwise. However, a couple of times while he and Rosie walked home after a late film at the cinema, he could have sworn he glimpsed a furtive tall figure trailing them, then dissolving into the night.

The phone's ringing jarred John awake. He rolled over, reaching for the receiver in the darkness. Rubbing his eyes, he mumbled, "Hello?"

"Dr. Watson? This is the transplant coordinator. We have a kidney for Rosie."

John sat straight up in bed. "What?"

"Yes, Doctor. A cadaver kidney—accident last night on the M5. Looks like a match. Can you have Rosie here in an hour?"

"We'll be there," he promised, and hanging up, he leapt from his bed. Minutes later, he had Rosie dressed and they headed out into the quiet early morning. He couldn't believe it. A kidney, finally. They had hoped that he would be a match, since family members were always checked first, but it wasn't to be. So, three times a week, every week, for the last 3 months, Rosie had sat in a big chair, connected to a dialysis machine. She had been so brave from the very beginning, and John felt a lump in his throat when he thought of how proud he was of his daughter.

Two hours later, they emerged from the hospital entrance, completely dejected. The donor kidney had been infected with hepatitis, which hadn't shown up on initial testing, so with many apologies, the staff of the transplant department had turned them away.

Molly Hooper was finishing a report when the pathology lab's doors burst open, and Sherlock pushed through, a determined look on his features. "Sherlock!" she exclaimed. "What is it?"

He approached and leaned on the lab table. "I heard," he said. At her perplexed look, he added, "About Rosie. Mrs. Hudson told me." Removing his coat and jacket, he rolled up his sleeve. "She said that Rosie has been considered for transplant. I want you to test me as a potential donor."

"I'm more than happy to test you, Sherlock, but you know as well as I that it's highly unlikely that you'll be a match."

"Doesn't matter," he declared stubbornly. "If there's a chance that I can help, then I have to do it."

Molly had to smile at his willingness to do so, despite the total lack of real contact between the detective and his friend and goddaughter. She gathered equipment for a venipuncture, and as she wrapped a tourniquet around Sherlock's upper arm, she asked, "Are you still following them when they go out at night?"

"Sometimes," he admitted. "I keep a weather eye out. You and Mrs. Hudson have both been occasionally helpful in letting me in on their plans…and the homeless network watches their house for me. Billy follows them when I'm on a case."

She found a vein and slid the needle in. He didn't flinch. Loosening the tourniquet, she added, "Have they ever noticed you, after all this time?"

His nose wrinkled up as it usually did when he was shocked/disgusted. "Molly Hooper," he said, "There's no need for insults." A corner of his mouth turned up ruefully. "Actually," he said, "I think John may have noticed something, a couple of times, but he never turned back to confront me, just kept walking." As Molly removed the needle, he held pressure to the site. "Did I tell you," he asked her, "that I kept them from being mugged on three separate occasions?"

"You're their guardian angel," Molly said warmly, squeezing his hand.

Sherlock snorted. "I've always been on the side of the angels, just never thought I'd be one of them." More seriously, he continued, "It's the least I can do. Try to protect them, whenever and however I can." He slipped on his jacket and retrieved his coat. "Just don't tell John that I know about this…please."

She nodded reassuringly. "I won't. I'll let you know the results soon, but don't expect anything."

"Coming around the flat later?" he asked.

"Sure, I'd like that."

A week later, John received another call from the transplant coordinator. A living donor had been found, she said, and this time, no infection, and even better, the match was perfect. John was happier than he had been in months. The next day, he and Rosie sat in her hospital room as the nurses prepped her for the procedure and the transplant surgeon performed an examination.

"Will we be able to meet her donor?" John asked.

The surgeon straightened from her exam. "Well, there's the rub. The donor wishes to remain anonymous."

"Anonymous?" he repeated, perplexed.

"I know," she said. "Weird, innit?" Turning to Rosie, she smiled. "Well, Rosie, you look marvelous. And you're going to come back here after surgery doing much better."

Rosie bounced up and down where she sat on the bed. "A new kidney, Daddy!" She squealed. "No more dial..ysis! Where are they gonna cut me open?"

The surgeon pointed to Rosie's stomach. "Just a little cut right down here," she said. "It'll be really easy. We don't put the new kidney where the old one is, that's up in the back. You'll get better straightaway from the surgery. In fact, the person who's giving you one of their kidneys has a much tougher surgery to go through. We have to get their kidney out of their back."

"Their back? Wow!" Rosie gasped, eyes wide.

"Ready to get this over with?" the surgeon asked.

"Absolutely," said John and Rosie together.

That night, John sat beside Rosie's bed in the darkened room as the monitors beeped quietly. She looked so small in the bed, but there was color in her cheeks, she slept peacefully, and John was content. Well, sort of content. The identity of their mysterious benefactor was still nagging at him. He looked across the room where Mrs. Hudson sat reading a romance novel.

"John?" came a voice from the door.

He turned to find Molly framed in the entrance. "Molly!" he exclaimed in a whisper. "Please, come in." He beckoned her to Rosie's bedside. It was then that he noticed her somewhat drawn expression. She looked tired and worried.

"How's she doing?" Molly asked.

"Just fine," he answered. "Should be up and about tomorrow. She's on her anti-rejection drugs, and the transplant people think she will do very well."

"I'm sorry, what?" said Molly.

He repeated the news to the distracted pathologist, and she smiled back at him. "That's wonderful, John. Um, look…I…I've got to get going…I'll stop and see her again in the morning." She slipped quietly from the room.

John's eyes narrowed. Something was wrong with Molly. "Mrs. Hudson," he said. "I'll be back in a minute." He rose and followed Molly, hoping to ask what was the matter. He looked both ways down the corridor, and just caught a glimpse of Molly's ponytail as she rounded the corner. He jogged after her, tailing her down a flight of stairs and into another wing of the building. He peered around the corner to see her enter another room in the intensive care unit down the hall. John approached the door and slowly looked in. Molly, her back to him, had just seated herself at the bedside of…Sherlock. His breath caught as he realized his first good look at his old friend revealed that Sherlock was not doing well. He was unconscious, an ET tube in his throat, a ventilator forcing air into his lungs, and as John took all this in, everything suddenly clicked into place.

Molly heard his involuntary gasp and whirled in her chair.

"It's him, isn't it?" he asked. "Sherlock. He's the donor."

She nodded silently.

"What happened?"

"There was a reaction to some of the anesthetic…late in the surgery, after the kidney was removed," she replied, as tears sprang to her eyes. "He…his heart stopped on the table. They tell me they were able to resuscitate him quickly, but he hasn't woken up yet."

John looked from Molly to Sherlock's body, motionless except for the measured rise and fall of his chest. "Why didn't you tell me?" he asked.

"He didn't want anyone to know. Not even Mrs. Hudson knows, only Mycroft." As she noticed the softening of John's features as he gazed at his estranged friend, she continued, "He only ever wanted to help, John."

She went on. "He came in last week, begging me to test him as a possible donor, so I checked it and he was. He's changed quite a lot, John. I mean, he's still an arse occasionally, wouldn't expect a total 180, but he is truly different. He bugged Mrs. Hudson and I constantly, always wanted to know how you two were doing. He used to find out when you were going out at night, just so he could keep an eye on you. Got in a couple of fights with potential muggers, too. He's been your guardian angel, though he'd never call it that." She smiled sadly.

And John bowed his head, suddenly realizing just how much he had missed this man. His rage had smothered him. For years, his anger at Sherlock had alternately smoldered and flared, as his grief for Mary had been most palpable. He heard again his own voice from the past—you made a vow! He had told Molly to push Sherlock away, to tell him that he would rather have help from anyone else…anyone. And that had been the most painful thing of all.

"Molly…I…I'm sorry."

"For what?" she asked.

"For asking you to say those cruel things. It was unfair to you."

She said gently, "It was unfair to him, John."

He nodded. "Mind if I sit here with you for a while?" he asked.

She pulled a chair over to join hers. John sat down, and the two of then maintained their vigil.

The first thing Sherlock noticed was muttering voices, and then a terrible soreness of his chest wall, then pain in his back where they had removed his kidney, then the troubling sensation of the ET tube in his throat. A wave of panic swept over him, but a warm hand took his and he heard Molly's voice. He looked to his right and her face swam into view.

"Sherlock, it's all right. You're okay." She squeezed his hand in emphasis.

He pointed to the tube.

"That's the vent tube, Sherlock, they'll get it out soon, I promise. I'll tell your nurse you're awake."

She was true to her word, and within a couple of hours, the tube was removed and he was much more comfortable. Molly had remained with him, and then Mrs. Hudson arrived, hovering over him tearfully, saying he was "a dear" for helping Rosie. Mycroft and his umbrella stopped by mid-day, just long enough for a few choice barbs. It was then then Sherlock knew he really was recovering, since his brother was his usual cynical self.

But the very thing that he had desperate for, through those long years of waiting, rolled through the door of his room that afternoon. As Molly's eyes shined with unshed tears, his old friend John pushed his goddaughter Rosamund Mary Watson into the room in a tiny wheelchair. John halted, staring, as Sherlock gazed back warily, trembling, not daring to hope.

Then John's mouth quirked upward in a genuine smile, and in that smile there were apologies by the score. "Rosie," he said, "I want you to meet your godfather."