Author's Note:-
I wish I could take full credit for this angsty masterpiece, but this is actually just the narrative version of a comic by TheBombDiggity666, you can find it on her deviantart page. I really love reading this comic, so much that I had to have a go at writing it into a fic, which is a first for me as I've never narritised a comic before. I've also never written an idea that wasn't my own before… so a lot of news here.
Anyway, I tried to use my best articulation with this piece (which I rarely do for fanfics, so another first!), and I hope I did it justice. If you like this, please head over to TheBombDiggity666's DA page and look at the comic because it is amazing.

Click. The door closed, sending a timid echo through the vast, empty hallway of the Skelefam house as Dr. W. returned home from a busy night in his laboratory, much later than he'd planned. Always a hard-working man, it was not the first time he had stayed behind after hours. Gaster had a passion for his work and a keenness to finish what he had started, and the unfortunate consequence of such bittersweet attributes was, amongst others, that he sometimes arrived home at an unsociable hour.

He stepped into the hallway, accompanied by his youngest son Papyrus, who was carefully positioned on the tired professor's shoulders. He kept a firm grip on Papyrus's legs as he called into the dark depths of the house, to his eldest child.
"Sans!" Gaster's voice echoed off the cold walls, travelling through the building like a phantom through its chamber. "We're home, sorry that we're so late!"

Papyrus squealed slightly at the sound of his father's voice, becoming excited by the noise and his new surroundings. He looked around the hallway in awe, fascinated by the familiar sights of his home. He grinned to himself, and playfully clutched his father's skull with his gloved hands. Papyrus was almost entirely covered in thick winter clothing, to protect his young fragile bones from the bitterness of Snowdin's cold. Today was particularly spiteful. Only Papyrus's face was exposed, and his playful grin grew even wider upon it as Gaster started to lift the toddler from his shoulders.
"WEE!" Papyrus giggled as he found himself carried through the air, above his father's head and down against Gaster's chest, held safely in the scientist's steady arms.
"It was a late night at the lab…" Gaster continued to speak to the seeming emptiness of the building, and a subtle brush of guilt crept through him as he glanced at the clock on the wall. 18:40. As expected. Gaster knew he was late, but in rushing home his journey had been shorter than usual. He was discreetly pleased with how quickly he had arrived. Still… regardless of that, it was a long time to leave his eldest child alone, when Sans would have expected him back over an hour ago.

Gaster waited for San's response, expecting the boy to reply with some foolish remark or childish pun, much to the disapproval of the stern Dr. Gaster. However… there was nothing. There was nothing to greet the doctor except the sound of the clock ticking on the wall… and bar that, silence. This was rather unusual… "Sans?" Gaster uttered, raising his voice slightly with the assumption that he had simply not been heard. "Are you here?" Still nothing. The house was silent, but for the rhythmic tick tocking on the wall. "That's strange…" Gaster thought to himself, becoming slightly unnerved by the unexpected quietness of the building. "He should have been here hours ago."
"BA?" Papyrus uttered, sensing his father's growing discomfort. He looked up at Gaster, seeking some sort of positive response from the man, or a change in the staling atmosphere. Gaster however had other things on his mind.

He set the bewildered toddler down on the floor, and Papyrus landed with a soft plop on the dark carpet.
"Go play, Pap." Gaster instructed, already taking his eyes off Papyrus as he gazed up the long, steep flight of stairs. "I'll be back in just a moment."

He left Papyrus alone in pursuit of his eldest child. Gaster started to make his way up the stairs, his boney fingers lightly grazing against the varnished wood of the staircase as he feared what was about to come. "Come on, Sans." He thought to himself in exhaustion, too tired and too drained to play this irksome game once again. "Don't make me search the whole Underground for you again." He dreaded that. Truly. It was such an inefficient use of time – such a waste of valuable minutes and seconds. Gaster didn't care much for time wasted, nor did he care much for defiance or trickery… and especially not now. Not when he had just returned from a long day at work, and he wanted nothing more than to put Papyrus to bed and settle down for the evening. "We can't keep doing this." He sighed silently, almost groaning to himself as he reached the top of the stairs and approached Sans's bedroom door. "I can't keep doing this." Yes… That was much more accurate. Perhaps this was all good fun for a young boy, but Gaster failed to see the amusement in this. "Sans." He spoke sternly, his frustration and impatience ever so subtly creeping into his monotone voice. Gaster placed his palm around the door handle, his annoyance at the situation reaching its brink. "Why will you not answer me?" He turned the handle, hoping that Sans would at least be in his room, even if he refused to talk.

Gaster pushed against the door ever so delicately, as discreetly and respectfully as he made all of his movements. The slight pressure of his weight caused the door to creak and groan, almost screaming as it was opened. From its tired hinges it let out one final moan, and obediently granted W. access to the darkness that was on the other side.

To be continued...