It happened on an ordinary day, under snowy trees in the wind-whistling depths of Snowdin forest. Sans sat down at the mysterious door, rapped knuckles against it, and told his newest zinger — the one about the cat monster who wouldn't stop kitten around. Pretty solid material, he thought as he waited for his friend's wonderful laugh.
But all he got was a limp chuckle. It didn't sound like her at all.
"Hey," he asked, "you okay? You sound down." It was early in the timeline for that; he never made the guardian promise to her this early and anticipation rose sour in his throat.
"Oh, it is nothing serious," she said. "I must say, though, that I feel badly. We have delightful conversations and throughout them all, you are outside in the cold. That is a rather rude way for me to treat a friend."
"That's all? Aww, hey, lady, don't worry about it," Sans said. His grin widened with relief, and his head tipped back against the door but he kept the ease in his voice because he never couldn't. "The cold doesn't bother me because I'm so … chill."
There was her laugh, bursting out shrill and delighted. "Still! I am unintentionally giving you, um. A cold shoulder! I wish there was something I could do …"
"You could always open up this door? That's knob too much to ask."
She went quiet again. The wind whistled in the bare treetops.
"I cannot do that," she said soft. "I must stay here, and it is forbidden for anyone else to reenter these ruins."
"Y'know something? I've never been in the ruins. Never even walked through this door here. So it's impossible for me to reenter."
"Really? You didn't come from—" She bit off her words so hard, Sans could practically hear a click of teeth. "Ah, well. That may be, but regardless, no one can enter this door. There is a direction-sensitive spell contained in this threshold. I cast it many years ago. Leaving the ruins through this door is permitted, but opening the door with the intent of entry would be quite impossible."
"That's no problem," Sans grinned. "If you're actually inviting me inside, I know a shortcut."
"You … what? That is, I would love the company, but …"
Oh, Sans did like an easy challenge. He got to his feet and brushed the snow from his shorts. "Tell me, lady. What's it look like on your side of the door?"

He wasn't stupid enough to try teleporting blind, so he had to coax a careful, thorough description from her. She was standing in a very long, straight hallway, about fifteen feet wide by twenty feet high, its purple stone surfaces bleached by time. Combined with the echo he remembered when she laughed loud enough, and his best guess at how thick the door was, Sans got it all laid out in his mind.
"Perfect," he told her. "Knock knock."
"Who is there?" she replied, eager.
"Turner."
"Turner who?"
A flick of his magic and Sans was inside, walking up behind her on soundless slippers. His friend was tall and round-edged, hunched against the door and pressing an ear to the outside, her other long ear blanketing her face and blocking her peripheral vision.
"Turner 'round," Sans said, "I'm right here."
"Oh!" She whipped around, paws rising to her mouth, thick-lashed eyes gone wide. "Oh, my goodness! You can— Ah." Her shock was dissolving into a toothy smile, wider and wider across her snout. "Hello!"
What a priceless face. Sans couldn't help but laugh — really, honestly laugh — at the feeling like happiness within his ribs. "Hey. S'great to see ya."

Once she grasped his hands and assured herself that Sans was really there, and finished grinning excited at him, they introduced themselves for the first time. It was like swallowing a pill. Just a matter of accepting her name and ignoring the memories of a past queen. Toriel squinted a little at his name, clearly remembering staff rosters and clearly unused to guarding her thoughts; Sans kept his poker smile on. She took his hand again and somehow, that made it less weird as they headed deeper together into the ruins.
Their history didn't matter. She was just Toriel now. He was just Sans. Her paw was a big, warm mitten around his hand bones and her physical magic crackled against his own like the static in a woolen sweater. In this moment, they were just two monsters who liked making terrible jokes in the dark— and, as it turned out it, they had even more than that in common. They both had a taste for butterscotch.

So after an hour or so of Toriel bustling around, cooking in her cozy little kitchen, she cut Sans a big slice of the gooiest, most fragrant butterscotch-cinnamon pie he had ever seen and she poured him a steaming mug of tea to go with it.
"Toriel," he said through a heavenly mouthful, "this is the best thing I've ever eaten."
"Really?"
"You butter believe it."
She spluttered on her tea, and laugh-coughed politely into her fist. "That is very kind of you to say, Sans."
"No, I mean it." He shovelled in another bite and added, "I've been trying some of the pies we talked about but I can't make 'em come out right. Hey, do you have a recipe for that spinach egg pie? I figure it might help if I actually read the recipe." Sans was more of a numbers guy than a touchy-feely guy, after all.
Beaming and clutching her mug tight — while blushing rosy under her white fur, oh god that was cute — Toriel nodded. "I have a large collection of recipe books if you would like to see them. Actually, while I am at it, there is a fascinating snail fact I would like to share with you!"
By the time he topped off his mug of tea, Toriel returned with a ragged-edged stack of books. All of them looked like they had been read a million times; most of them had seven or eight bookmarks poking out; some had handwritten titles on their cracked spines.
"Did you know," Toriel enthused, "that snails have tooth-like structures on their tongues, which they use to scrape up food? I suppose you could say …?"
Getting an assist on a terrible pun? Now Sans was just being spoiled. He propped an elbow on the table, leaned jawbone onto palm, and replied, "That snails have grating personalities?"
"Yes! I just knew you'd make a good punchline for that. One moment, please — I must write it down." And then Toriel left, calling out melodiously that the spinach egg pie recipe was on page 74 of Wholesome Baked Dinners.
Well, if she had the page number memorized then she must have /made/ the recipe an awful lot, and Sans figured she burned pies less often than he did. When Toriel returned with a journal, Sans was running a phalange-tip under the recipe's direction to finely dice the ingredients.
"Hey, Tori?"
He hadn't meant to call her that: it just sort of slipped out. The bright smile she turned to Sans made it better and yet worse.
"Yes?"
"Heh, you like that, huh?" He smirked and tried to ignore the embarrassed magic glow in his cheekbones. "I guess you don't get many people nicknaming you in here?"
"No, I do not! There are other monsters in these ruins, but they appear to be afraid of me."
That was sad, and unfair — and geez, kind-souled Toriel said it with a press of her mouth like it was a simple fact of her life. She was jotting down the snail tongue joke and carefully underlining the grating punchline, so it took a moment for her to glance up at Sans and wordlessly question his silence.
After that first dishes joke through the door, he had gotten the impression that this lady was lonely. Seemed like he didn't know the half of it. Seemed like Sans could ask this friend about her troubles and maybe even share some things rattling around in his own head — but that was a dangerous place to let his hopes go. Sans had learned his lesson enough times already.
"Heh… Anyway, Tori." He tapped his phalange on the cookbook page. "This part of the recipe, where it talks about finely dicing the egg pie ingredients. How fine are we talking, here? I think I've been cutting 'em too big."
"Oh, I can show you, if you would like?" She didn't wait for an answer, standing and reaching for her flour-spotted apron. "Maybe I should just make the entire recipe. The baking time can be tricky to get right, as well."
"You'd make another pie for me? You're sweet. Like— Well, like a pie."
"Pie jokes! Just one moment, I have something for this." She lifted a clawed finger, and she darted her gaze around while she thought, and she gave up and sneaked a peek at a page of her journal."I will bake you as many pies as you would like, Sans. Crust assured!"
Maybe, he corrected himself, he'd spill his guts to her someday. Or at least tell her she didn't deserve to be lonely. Not right now, though. He sure didn't want to rain on her pie-rade.

Toriel rolled more dough, and made it into a spinach egg pie with sure-moving paws, and brought the finished product out of the oven looking impossibly perfect. Sans had another steaming, heavenly slice to eat while she sat beside him at the dining table and started describing her favourite snail pie. She opened up an encyclopedia to show him the exact right kind of snail to use, and show him information about snails in general, their lives and habits and flavour profiles.
Snails weren't Sans's favourite food — or even one of his top fifty favourite foods. But Toriel was aglow with enthusiasm and all he had to do was listen and throw in the occasional shell pun to keep her grin going. Sans found a paper napkin and a golf pencil in his pockets and started taking down the baking tips from earlier. And at one point he scribbled out a misspelling and doodled it into a weird, scribbly snail; Toriel leaned over, grinning, and took the pencil to add a second, more elegant snail with curly eyestalks and a smiling face.
"There," she said. "Now he's got a friend."
Yep, Sans thought as he grinned wide and honest, that was exactly what it needed.

With the lack of ceilinglight in the ruins, Sans couldn't have said how long he stayed. But he told about a dozen stories about Papyrus's adventures in spaghetti, and the teapot went cold, and Toriel's voice got hoarse edges from doing a month's worth of chatting and laughing in one shot. Sans had to yield to the inevitable.
"I should get back to work," he said, pushing back his chair.
"Please, allow me to see you back to the door."
"Still worried I'm going to get lost? That's a nice gesture, Tori. Giving me a hand like this." With a wink, he offered his hand for holding.
"I am a hands-on ruins guardian." She wrapped his hand with hers again, warm and alive.
"So, Sans, you were working?" Toriel asked while they walked. "Will you be reprimanded for your absence?"
He shrugged. "It's fine. I was on break. Then I was eating pie, so that was my lunch break. And after that, I was on my third and final break. Union rules, you know."
"Oh, you're unionized? Good."
"I work as a sentry. Don't think I've told you that yet, huh? It's not a bad job — and hey, I'm stationed right by that door of ours."
Toriel hummed. She watched the floor passing under their feet. "I do wish," she murmured, "that you could stay."
Sans wanted nothing more than to stay here. To chat and joke with her for days, to fall asleep in that comfy-looking chair by the fire with some light biology reading in his lap and wake up to the golden aroma of pie crust and the sight of fondness in her eyes, and to feel the unsullied joy of right now. What was stopping him? Why couldn't he take one cycle for himself and just live?
"I'd like to stay, too, but there's work to be done," Sans muttered. "And Papyrus. I can't leave Papyrus."
"I did not mean actually keeping you here," Toriel said in a voice like wilting flowers. "I meant … Well, I am not sure what I meant. Pardon me, I am being a silly lady."
"No," Sans said, "no, you're not." But he wasn't much good at comfort anymore: he couldn't find more to say.

They reached the end of the hallway, their footsteps echoing away to nothing. The door loomed ahead, a door that could only be walked through in one direction. He would see her again, in this timeline or another one; that was no comfort.
"Well," Sans said, shifting his slipper soles against the stone floor. "I entered the ruins, so I can't enter again. I guess this is goodbye. Sure hope it's not goodbye. Maybe it's see-you-later."
Toriel knelt and he was enveloped before he knew it, wrapped up in her arms with her yielding cheek against his wide-eyed skull. He squeezed her in return, his own arms only reaching halfway around her robed waist, and then began to release. But he froze because the hug somehow wasn't over. Toriel was still there. She just held him. Held him close so her body heat soaked into his bones and her magic laced with his like they knew each other for real, while her heartbeat reverberated in his hollow chest. Her breath filled her soft-fleshed body over and over, flowing out to rest warm between his vertebrae. She was here and she was lonely, too, and she cared and he cared, too, and that made something well up from Sans's marrow, made him squeeze his eyesockets shut against tears. This was nearly as right as Papyrus's hugs.
"This is certainly not goodbye," Toriel whispered against his skull. "Please keep visiting me, even if we cannot be in the same room. Whenever you have new jokes to share, I would love to hear them."
"Will do," he rasped.
"And please give your brother a hug on my behalf. He sounds wonderful."
"Sure thing, Tori."
She let go, finally, to grip his shoulders and give a last shining smile. "Be well, Sans. Thank you. Thank you."

The door boomed closed behind him. Sans was back to staring at his own footprints in the snow, combing through memories and trying to keep the happiest ones closest to his soul. After a last glance at the unmysterious door, he turned back toward his sentry station, snow crunching underfoot, fresh powder drifting down around him through ordinary forest.
Someone like Toriel was worth bending the rules for. If nothing else, Sans was sure of that. Maybe that was why, in every timeline, no matter how doubtful and hopelessness he was, Sans always promised when she asked him to.

In one curled hand inside his pocket, he held a paper-wrapped slice of butterscotch-cinnamon pie. In his other fist, he held the note-covered scrap of napkin. His timeline notes were getting some personal footnotes tonight — even though he would never, ever forget.