Tahoma hadn't realized what giving Sans his old stethoscope could lead to. It had just been cute at first, seeing him run around with the stethoscope looped around his neck and dangling nearly to his knees, trying to pick up a pulse from inanimate objects, listening to the pulse of his own soul, checking Tahoma's every few minutes 'in case it changed.'

"Are you going to be a doctor like your daddy when you grow up?" he'd ask, and smirk at Eras when Sans said yes. Eras would play along, pretending to be annoyed. Sans was certainly bright enough—he had a tendency to lose interest in things which he didn't see the point in, but that was completely understandable for a kid. Of course, reading was far from pointless, as they were trying to convince him. It had worked, sort of: he could read the children's books at home very well, but when told to read in school, he'd roll sideways out of his chair and start playing with his jacket zipper. He was great at math, though, and mad for any kind of science. What really convinced Tahoma that he had a tiny scientist on his hands was his passion for asking question. Why does this work? What is that? And finally, "Why is your soul louder than mine?"

He hadn't been prepared for that one.

"Because I'm bigger than you," he'd said, without thinking about it, and Sans had accepted that and moved on. That had been a while ago. Tahoma had almost forgotten about it, and he certainly hadn't expected Sans to remember, but it seemed he had.

Sans tugged on the tail of Tahoma's plaid shirt until he looked down.
"I was listening to Papyrus's soulbeat today," he said, very seriously. Tahoma sank down to his knees, which put him more on Sans's level—he was short, even for his age.
"And it's louder than mine is."
"Really?"
Sans nodded. "But you told me yours was louder than mine because you're bigger." He looked searchingly at Tahoma.
Well chisps.
Um.
"That's one reason," said Tahoma. "There are a range of things which can effect how well the stethoscope picks up the soul pulse."
"But you just said it was because you were bigger." Tahoma nodded. Sans stared at him.
"I don't have to tell you everything about everything at once, do I? That's a tall order. Unlike you, shorty."
Sans didn't smile with him.
"It's unscientific to draw conclusions based on incomplete information," said Sans sourly. "Right?"
"…Right." Usually he would praise Sans for remembering something like that. At the moment, it was incredibly inconvenient. A stifled snicker from the doorway behind Sans told him that Eras was watching, and that she was unsympathetic. Traitor.
"So why is his louder than mine? He's smaller. He's really, really small. It should be quiet."
"Well, as I said, size isn't the only factor…."
"Yeah?"
"Actually, size is usually a fairly minor factor."
Sans nodded. He looked annoyed, but he wasn't saying anything. Tahoma scrabbled for words.
"Papyrus is stronger than you."
"But he's a baby."
"Well, yes. He can't walk yet, so you're ahead of him there, but he's stronger than you were at that age."
"But it's still louder than mine? So is he stronger than I am now?"
"Um, sort of? His soul is very strong, and it has a strong bond to his body."
"So, am I not strong?"
"Well."
WHY WAS THIS HAPPENING NOW? OR EVER?
"It's a bit early to say, your soul will change as you grow, but well no, not really. Have you noticed it's much easier for you to get hurt than the other kids at school, and mom's always telling you to be careful?"
"Yeah, you said that was because I was a skeleton."
Oh whoops. Again Tahoma cursed his past self.
"Well—I think what I said was, one reason why your bones get cracked more easily is because they don't have any tissue to protect them, which is true—"
"But I wasn't asking about that, I was asking why I get hurt so much."
"Well, I—"
"Did you lie to me?"
"No! I wouldn't lie to you, Sans. I just withheld some information. I can do that." Why did Tahoma feel like his son was judging him for all of his sins?
"You didn't answer the question I was asking you."
"I'm sorry."
"So why do I get hurt so easily?"
"I… Honestly, I don't know exactly why, but you've always been like that. You nearly died when you were a baby like Papyrus."
"Really?"
"Yeah. So, since then we've been really careful"
"Wait, why did you never tell me this?"
"I never got around to it. It's not a happy story, after all. Except for the part where you lived, of course! That part was happy." Please don't ask for the whole story right now, I need to calm down and think out how I'm going to say this. "You know how your mom or I will check your HP before bed every night?"
"Yeah?"
"Have you noticed we don't do that for Papyrus?"
"Mom does sometimes. She comes in when he's asleep to check on him."
Tahoma looked up at Eras, still standing in the doorway. Her face was blank.
"Really? Well, we do that to make sure it isn't getting too low, because you don't have much."
"Why not?"
"It's just how you are. OK?"
Sans seemed to think this over. "OK. What happened when I almost died?"
"Can I tell you later?"
"When?"
"Tomorrow?"
"Alright, I guess."
"Cool beans. Hey, do you want to see your soul?"
Sans looked interested.
"Can you do that?"
"Sure! Take your shirt off." He did, and Tahoma placed his fingertips on Sans's sternum, then gently pulled with his magic. Sans's soul floated into view. A nice regular pulse, he noted. The outline was very bright, fading to a duller white inside, almost but not quite translucent in the center.
"Pretty, isn't it? See, there's nothing wrong with it. It's lovely."
"What does yours look like?"
"Hm? Oh, you want to see mine? OK, can you hold it for a minute?" Sans put his hands inside Tahoma's and Tahoma tried to shift the soul to him. It wasn't easy to hold a soul. But Sans was good at magic, and he was proud, but not surprised when he felt Sans take hold. He pulled his hands away. "Hey, good job! That's not easy. OK, one minute—let me just—nmghh." He got tangled in his jacket. "How many layers am I wearing?!"
That was a cue for Eras to laugh at him, but she didn't, and he realized that she had left. He finally wiggled his arms out of his jacket, plaid shirt, non-plaid shirt and sweater, then shrugged off his T-shirt. For a brief moment he wondered why he did like wearing so many layers. Heat wasn't an issue for him. Maybe it was a substitute for mammalian tissue. There really wasn't much of him there when he wasn't wearing clothes. Maybe he'd started doing it so there'd be more to him, and he'd be less easy to lose in a crowd of mammals. And it made him much less unpleasant to touch for fleshy monsters. But lately he seemed to compulsively gain layers over time whether he 'needed' them or not—he'd see a shirt that he'd thrown down somewhere and put it on. Better than leaving it on the floor, right?
He looked up—Sans was still holding his soul. Was this a good idea? Too late, they were doing it. It seemed it was time to stop shielding Sans from the truth. Tahoma pulled his soul outside of his ribs.
"Woah," said Sans. "It's so big."
"I'm big. Your soul grows with your body."
"But it's so bright."
"Yep! Souls have different qualities, though they're generally all white. Some are brighter, some are less bright." There you go again, skewing the information… Some souls are brighter, but Sans's is on the dull side by any standards. He'll probably figure that out by himself eventually. They teach them about souls in school, right? …was he being a coward?
"OK," said Sans, staring. His own soul had slipped back into his ribcage. Tahoma suddenly realized how quiet the house had gotten.

Sans had gone back to playing, and Tahoma went into the kitchen and found it empty. A pot of something was sitting on the back of the stove keeping warm. She'd left the faucet dripping and a cutting board out on the counter. He turned the water off, left the room and climbed the stairs.

He found her in the bedroom, sitting balled up on the bed, chin on her knees. He climbed up and wrapped himself around her, taking her hands in his own and running a thumb over the slender finger bones.
"Heya."
"You told him."
"Yeah. He was asking, I figured I should."
"Did you tell him what happened after he was born?"
"He demanded to know, naturally, but I've been granted a reprieve until tomorrow."
"Good." She turned and buried her face in his shirts. "Don't tell him I gave up on him."
"What? Hey, hey—" Her body shook with silent sobs.
"I would have let him die."
"No, you wouldn't! Besides, that's a hypothetical, and therefore unimportant. Sans is fine. So is Papyrus. Papyrus has enough HP for both of them, Heh. He'll protect Sans when he grows up. They'll protect each other. It'll be great. You'll see."
"I'm shit."
"Dear! No you're not! I can't understand what you must have gone through. It was awful. But it's over now. Everyone's OK." He rubbed her back and they sat for a while, Eras gradually calming. "Do you want me to finish dinner?"
"Ha! Is that supposed to be comforting?"
"Hey, I can cook alright if I need to."
"Let's not test that. It's mostly done anyway."
"Well, good. What would we do without you?"
"Starve. Otherwise you'd be just fine."
"That's not true. You're twisting the truth, you do that when you get upset. You know it's not real."
"So do you, mister. I heard Sans read you the riot act about withholding important information."
"I…That's different… alright, fine." He snickered. "That kid, eh?"
"Mm-hmm."
"If he doesn't solve quantum physics or something when he grows up I'm going to be disappointed."

When he came downstairs, he found Sans hanging over the side of Papyrus's crib, gently holding the chestpiece of the stethoscope against his back. Papyrus was awake and flailing, but not crying—yet. He got excited for mealtimes. Tahoma lifted him out of the crib, and the flailing intensified.
"Ready for dinner?" he said. Papyrus kicked madly, giving a few impatient coughs, like a motor getting started. "Alright, alright, we're ready for you. Don't lose your head. Nothing moves fast enough for this little mon, does it, Sans?"
Sans grinned up at him.
"You can hear more of it."
"Huh?"
"You can hear more of what his soul sounds like than mine. Mine is like just a little click, but his sounds like thumping, and it sounds like it lasts longer."
"Well—yes, it's louder, so you can hear more of it so—yes." He'd hoped they were done with this, but he liked Sans to be curious, and really, he couldn't expect him to forget something as interesting as this in half an hour. Of course, he probably didn't realize how much it meant to him, how universally it would affect his life. Or maybe he did. Sans could be hard to read.
"Can I listen to yours again?"
"I—sure. Let me get this little tyrant something to chew on before he has a fit."
"Nyeeeeeh!" protested Papyrus, bouncing up and down in his high chair, but stopped after the one exclamation. He was in a good mood tonight. Tahoma only had to offer him five pieces of carrot before he picked one and began crunching on it, drooling ectoplasm out of the corner of his jaw. Tahoma pulled his own chair out and slumped in it, realizing all at once, as the weight left his body, how tense he was, and how nice it felt to really sit down. He relaxed, letting his bones hang limp.
"Alright, Dr. Sans, we're ready for you."
Sans climbed into his lap and pressed the chestpiece into his shirt, listening quietly. Tahoma half-closed his eyes.
"Has it changed?" he asked when Sans lowered the stethoscope.
"No." he snuggled against Tahoma's chest. "I like your soul. It sounds like music."
"Why thank you. You know what I like? I like your socks. And your eyes, they're pretty. I like everything about you, Sans. I even like it when you steal my shirts. Just don't take my favorites."
"Which ones are the favorite?"
"Um… probably the ones I'm wearing."
"OK."
Tahoma laughed, nuzzled the top of Sans's head and let his own head hang back. It was nice, being home. This was nice.
He had to be shaken awake for dinner, and afterward he fell asleep with his head on the table. Everything was quiet and warm, here. Everyone was OK. And he realized, in the lightning fast way that such things usually hit him, that he was tired.