A/N: all of the medical jargon comes from an episode of House ("All In" - it's in season 2) because I do not know how to disease, also the plot kinda comes from there too

"New case for you, Doc," the nurse from the station in the ER called out. Regina walked over to the desk and took the offered clipboard.

"What do we have?"

"Patient Henry Swan. Seven years old. Mom Emma Swan noticed blood all over his pants while they were out at the park."

Regina glanced at the charts in her hands, her eyebrows furrowed. "Henry Swan? I thought he was Whale's patient."

"He is," the nurse said. "Whale called out for the day." She handed over another clipboard. "They just need your signature to go. Simple case of bloody diarrhea. He's already been put on fluids—"

Regina stopped. "Bloody diarrhea?" The nurse nodded. Regina started walking towards the room listed on the chart. She entered the room with her usual heir of confidence, marching right past the blonde mother and over to the brunette child laying on the bed.

"Follow my finger," she commanded, moving her finger from side to side in front of the child's face.

His eyes followed her finger, but they were much more unsteady than they should have been.

"Excuse me, where's Dr. Whale?" the mother, Emma, asked as she walked over to stand on the other side of the bed.

Regina ignored her and held up her pen. "Grab my pen."

Henry's arms stretched outwards, grasping at the air next to her pen.

"What's going on?" Emma asked.

Regina finally looked up at the woman, brown eyes connecting with green. "I'm afraid you and your son won't be leaving her anytime soon, Miss Swan."

-—-

The lock clicked on the file cabinet and Regina slowly opened it, withdrawing from the bottom the old case file that had haunted her for years.

Bloody diarrhea. Coordination problems.

"It's not the same case," Dr. Kathryn Midas said. "It's just gastroantilitis. Once he's hydrated, he'll be fine." They both walked into the patient's room. Dr. Midas gestured towards Henry Swan, who was sitting up in bed and looked perfectly fine. "See?"

Regina narrowed her eyes at the patient, looking over him and his vitals. "He won't be."

"Would someone care to explain to me what the hell is going on?" the mother demanded.

Kathryn put on her most professional smile. "Nothing is wrong, Miss Swan. Dr. Mills just thinks—"

"Your son's brain is losing control of his muscles," Regina interrupted. "Next step is kidney failure."

"Next step?" Kathryn asked with a raised eyebrow. "Regina, it's just dehydration—"

"Really?" Regina interrupted again, stepping forward and picking up one of the bags of fluids connected to Henry. "And what is this?"

Kathryn's eyes widened at the bag, which was barely full and contained brown urine. "His kidney's are shutting down."

"But you can help him, right?" Emma asked.

Regina and Kathryn both looked at each other hesitantly. Kathryn put her famous smile back on. "We'll do everything we can, Miss Swan."

-—-

"Let's test for Erdheim-Chester disease," Regina told Kathryn after they left the room.

"Erdheim-Chester?" Kathryn asked. "No, it's too rare. There are only, what, 200 reported cases?"

"It's still a possibility. He had bloody diarrhea, ataxia, kidney failure—"

Kathryn stopped her with her arm. "And you think this magically means Erdheim-Chester? It could be anything— leukemia, sarcoma—"

"Then do a colonoscopy and prove me wrong," Regina said. "Because I guarantee you'll find purple papules."

Kathryn sighed. "Fine."

-—-

"It's clean," Kathryn said. "Purple blisters, yes, but no signs of the disease. "

Regina stared at the wall. "Run… a blood smear. I'll run an MRI and see if we can find lymphoma."

Kathryn sighed. "Regina—"

"Just run the damn test."

-—-

"Why is she taking pictures of his brain?" Emma asked as she sat outside of the MRI room.

Kathryn sighed. "Dr. Mills… thinks this case might be like one that happened a few years ago. She's just trying to confirm if it is or isn't."

Emma looked hopeful. "Well then if you know the case then you know how to treat it, right?"

"Not… exactly…" Kathryn said.

Emma crossed her arms. "Well then what do you know?"

"We know…" Kathryn slowly began, "…the course of the disease."

"The… course?" Emma asked tentatively. "What… what happened? To the last patient?"

Kathryn looked down before forcing herself to look the mother in the eye. "He died."

Emma put a hand over her mouth, tears coming to her eyes. Before Kathryn could provide her with a hopeful comment, Regina opened up the door to the MRI room.

"Miss Swan, I need you in here."

-—-

After helping to calm her son down and keep him still for the MRI, Emma was promptly sent out of the room. She was sitting curled up in a chair right next to her son's bed, watching him sleep while waiting for her son's new doctor to come up with a diagnosis based on the MRI.

Kathryn Midas walked in at that moment. "There were no signs of lymphoma in the blood cells."

"That's a good thing, right?" Emma asked, keeping her eyes on Henry.

"Yes and no. It's good that he doesn't have lymphoma, but we now need to figure out what he does have," Kathryn said, pulling up a chair on the other side of the bed. "We did find a small mass on the brain, which explains his low blood pressure… it all points to pituitary failure. Dr. Mills is looking into the next treatment." Emma nodded, trying to process what the doctor was telling her. Kathryn leaned over and put a hand on Emma's. "If anyone can solve this case, it's Regina."

Emma looked over at her. "Didn't she fail the last time she had this case?"

Kathryn shook her head and leaned back in her chair. "She wasn't the doctor for it. She wasn't even a doctor at all." She paused, contemplating something. "The patient… was her fiancé. Daniel. They were out sampling wedding cakes when he came down with the same symptoms as your son. The doctors tried… but they couldn't save him."

"Is my son going to die?" Emma whispered. She looked over at Kathryn with teary eyes. "He's all I have."

"Regina went to school to become a doctor because of what happened to Daniel," Kathryn said. "She hasn't lost a case yet, and I doubt she's going to start losing anytime soon." She smiled. "She's stubborn like that."

-—-

"How are you doing, Mr. Swan?" Regina asked as she walked into her patient's room.

Henry shrugged. "Okay, I guess."

Regina looked through his chart and checked the screens near his bed. "Your vitals are looking good so far, and your liver is doing just fine thanks to our treatment." She trailed off as she continued reading the clipboard.

"Liver?" Emma asked. "I thought it was his kidneys that were shutting down…"

"They were," Regina said, looking over at the mother before turning back to the charts. "Liver failure was the next step, and I prescribed a preventative treatment."

Emma nodded. "Right. The old case."

Regina looked up again. "I'm not letting your son die, Miss Swan."

Emma smiled, but before she could respond, Henry started rasping.

"I… can't… breathe…"

"Henry!"

-—-

"How's he doing?"

"He had to be put on a ventilator. Now we can add respiratory distress to the list of symptoms."

"One step more towards solving it."

"No, one step back. We didn't do anything except speed the process up. Now instead of twelve hours to live, he has two."

-—-

"If we run the labs for Kawasaki's Disease—"

Regina slammed down the clipboard. "We don't have time for labs! Henry's dying, Kathryn!" She started pacing across the room.

"I know," Kathryn said calmly. "Regina, you need to clear your head. It was fifteen years ago—"

"Sixteen."

"Obsession is dangerous," Kathryn said. "You're going to save Henry, Regina. You just have to keep your mind on him."

Regina stopped pacing. "His arteries."

"What?"

Regina started walking out. "We need to look into his coronary arteries."

-—-

This time, Kathryn was doing the procedure on Henry, and Regina was waiting outside with his mother.

She didn't like this part. In Med School she was told that she'd be a great doctor technically but not personally, because she wasn't good at bonding with patients. Some of her professors (and patients) accused her of having a terrible bedside manner. She didn't think that mattered as long as she got the job done.

"How did he die?" Emma asked quietly, shifting so her thigh rubbed up against Regina's.

Regina turned, startled by the question. "What?"

Emma looked over at her. "Daniel. How did he die?"

Taken aback, Regina opened her mouth but didn't say anything. "I… I don't—"

"Was he in pain?" Emma asked as a tear rolled down her cheek. "I don't… I don't want Henry to be in pain. I don't want him to suffer—"

Regina cut her off by grabbing the woman's hand in her own, much to her and Emma's surprise. "He's not going to die," she said matter-of-factly. "I promise."

-—-

"What's she doing now?" Emma asked as she stared into room where Regina was with her son.

"Dr. Mills is performing a biopsy," Kathryn explained. "We found a mass in the atrium. She's going to—"

She was interrupted by the beeps of the machines next to Henry as he went into cardiac arrest. Regina turned and yelled. "Code blue!"

-—-

"Regina, the biopsy almost killed him."

"He's alive Kathryn. And he's not brain dead. Besides, I got what we needed."

"And that's enough for, what, three tests? Maybe? What are you going to do if none of the diseases you test check out?"

"They will."

"And if they don't—"

"They will."

-—-

Emma was started as a cup of coffee was placed in her view. She accepted it and looked up to see Dr. Mills.

"He tested negative for histiocytosis," Regina said softly as she took a seat in the chair beside Emma, looking over at her patient. "And tubular sclerosis."

"What does that mean?"

Regina sighed, taking a sip from her own coffee. "It means we only have one more test with the sample I manage to get from the biopsy."

Emma looked down, trying not to cry again. They sat in silence for a few moments before Emma spoke up again. "You know, I knew something bad would be happening to me soon."

"You what?"

"It's… a curse I have," Emma said. "Every time something really good happens to me, something really bad happens too. Good thing: I was born. Bad thing: My parents abandoned me on the side of the road. Good thing: I became pregnant with Henry. Bad thing: His father left me with all of the money we had saved." She sighed and licked her lips, blinking her eyes rapidly. "I've been… struggling to make ends meet lately. A couple coworkers invited me to a poker tournament at this weird bar they go to. I only brought the money I was going to spend the next day for lunch, and I ended up winning the entire tournament. Not that it was that big to begin with, but it was something." She smiled. "Walked away with upwards of $800."

"And now you think Henry being sick is your bad thing," Regina finished. Emma nodded. "Well I can tell you from personal experience that none of this is your fault. No matter how much you think you could have prevented it, or done something more, or…" She paused and lowered her voice. "…or even how much you wish it was you lying in that hospital bed instead…" She cleared her throat. "Nothing will change the fact that you couldn't have prevented it, and you have done all you can to help him…"

Emma smiled sadly. "I could've prevented my win," she whispered. "I had two aces hidden up my sleeve."

"Cheating in an amateur poker tournament did not put Henry—" She paused. "Two hidden aces…"

"Yeah," Emma said with a shrug. "I used to have to cheat my way through games like that the foster system, I guess I thought I could cheat my way through this one, too, but—"

"Two hidden aces," Regina said again. She stood up, putting her coffee down on the chair and walked over to Henry's bed. "The disease is hiding." She turned to the blonde. "Miss Swan, you may have just saved your son's life." Without another word, she bolted out of the room.

-—-

"Erdheim-Chester disease? We already tested for that—"

"Diseases lie. Try it again."

"Regina, we only have one more sample—"

"Try it again."

…

"Oh my God… It's Erdheim-Chester."

"Start the treatment."

-—-

Regina slowly pulled the tube out of Henry's throat, pulling it away from his body and setting it on the tray next to her. "There, does that feel better?" He nodded and she smoothed a hand over his forehead. "There's someone who's very excited to see you."

The boy's eyes lit up. "Is it Santa?"

Regina laughed. "No, not Santa. Not for another couple of months." She turned her head towards the door. "You can come in now."

Emma entered and a smile lit up her face as she looked at her son sitting up in the bed. "Henry!" She engulfed him in a hug. "Oh, thank God you're okay."

"No need to call me God," Regina said sarcastically, a smile on her face.

Emma snorted, looking up at Regina over her son's shoulder. "Someone's a little full of themselves."

"I think I'm allowed to be full of myself when I save a patient's life," Regina said. "And technically he's not even my patient."

"Yeah, where is Dr. Whale?" Emma asked, looking around as though he was going to show up.

"He was out sick yesterday. Unfortunately, he'll be back today," Regina said.

Emma smiled. "Worried he'll come claim your victory?"

Regina snorted. "He wouldn't even dare to try. Henry may be his patient, but this is my case."

"Speaking of…" Emma said, trailing off as she looked up shyly at Regina. "You're not technically our doctor."

"Yes…"

"So… technically… if I wanted to thank you for saving my son's life…" Emma gave a small smile. "Would I be allowed to thank you over dinner?"

Regina's eyes widened in surprise. "Dinner?"

"Yeah, you know. People. Food. Sometimes conversation."

Regina stood with her mouth open. "I'm currently your son's physician—"

"You just said you weren't technically our doctor," Emma pointed out. She raised her eyebrows and tilted her head towards Regina. "So?"

"Technically…" Regina started, pausing for a moment. "I could accompany you to dinner after your son is given a clean bill of health."

Emma smiled. "So that's a yes?"

"You'd have to wait until all of his post-ops are done."

"That's fine with me."

"It could be months," Regina pointed out.

Emma smiled. "I'll wait."

-—-

"Have you ever thought that maybe instead of good things triggering bad things, it could be the other way around?"

"What do you mean?"

"Well… in your context, bad thing: your parents gave you up. Good thing: You grew up to be the independent, selfless woman that I love. Bad thing: Henry's father abandoned you, but good thing: You were able to raise Henry without having to give him up. Bad thing: Henry became sick, but good thing…"

"What?"

"Good thing: you met me."

"How do I know that's not the bad thing?"

"Emma!"

"I'm just saying, you steal my french fries all the time. And you hog the covers."

"I suppose I do. But I also saved your son's life."

"Mmmh."

"How about this one… bad thing: you let me steal your french fries and hog the covers…"

"The good thing?"

"Good thing: you marry me."

"…"

"…"

"…Really?"

"Really."

"Well, technically the good thing would just be us getting married."

"Is that yes?"

"Of course it's a yes. Now shut up and kiss me."