SOMEWHERE IN THE DEPTHS OF THE PACIFIC, WHERE THE LIGHT COULD NEVER REACH FAR BELOW, HIDDEN AMONGST THE ROCKS AND SEAWEED, THERE WAS A LARGE DOME PLANTED FIRMLY ON THE BOTTOM OF THE SEABED.

It was hidden from plain sight; nothing could easily detect it at those depths alone. Within the dome was a large structure, built like a city, but with no intention of housing anything more than what was already inside the dome. There were no glistening signs on any corners of the structure, barely any light at all inside. Nothing short could see through the dome or the structure's windows.

The dome had been abandoned for decades, roughly forty. No one remembered it was even there or even existed, even what it was originally for. Records of it had been destroyed or heavily sanitized, those who remembered it were silenced one way or another, and it seemed like no one would truly know what truly happened inside the dome.

Of course, there was some scattered stories about what went on inside the dome, some simple, some dramatic, and some plum driven insanity. Of those stories, there were still grains of truth in them.

It was built sometime during the late '60s after the first string of Cybermen scare, which resulted in the local governments coming together to decide how to properly defend humanity against the Cybermen. The idea was that the Cybermen could not detect the dome or what was inside it, that they could not penetrate deep within the depths of the Pacific Ocean for the dome without being crushed.

The dome garnered a nickname that stuck through the years, the Compound, as it was home to the scientific experiments done by the Hal Corporation of Science and Technology.

Within the first year, the Compound had discovered new technology that could in theory advance humanity's fight against the like of the Cybermen and anything else that threatened. However, by that time, the Cybermen upgraded and the new technology the Compound had was ineffective against them. The Cybermen were upgrading at a pace that could never be humanly matched and it was at an alarming rate, too. In a state of panic, scientists, researchers, the like scattered to try to come up with new technology that could fell Cybermen regardless of their upgrades.

Progress was slow and agonizing; there had been neither new progress nor new technology, not even a scrap of research that was feasible. In a fit of fear, the Corporation fired the head scientist and searched for new blood, someone to take the reins further than anyone had done. While it searched, the Cybermen had upgraded to be ineffective against gold and had become even more terrifying in the conversion process that also changed per cycle.

Eventually, the Corporation found a new candidate: Sofia Lamb. She was fresh out of Oxford, good education, amongst other things, even bringing new ideas to the table. Some of the ideas would become questionable, such as Sofia found that the way Cybermen worked was that they had no qualms claiming humans to convert.

Of course, with the fickle nature that is humanity, no government official worth his salt would allow the conversion of humans. However, Sofia disregarded their outcries by reminding them that the soldiers of war had to be broken down and rebuilt to be successfully capable of handling combat and that this was no different.

There were still outcries, mostly about the sheer thought about people suffering during the conversion, but Sofia silenced them, by saying that it won't be the case.

It came to a head when she invented a thick syrup substance that when used, would allow the machines of the newly formed project, Project Alpha, to be controlled with ease. No computers could do what her substance did and it was promising, much better than what the Cybermen could've drummed up.

Sofia never did say what the extent of her conversion process would go or how it would even begin. No one could've known what she planned as she was a person who kept secrets close and enemies closer. Even the Corporation had no idea what Sofia had in mind.

One faithful Halloween, the project came to a head. The projected output was considered nonexistent, but Sofia went ahead and as the stories went, she was undeterred. No one was sure in the stories gathered, some claim she had several people taken at random as means to experiment on, while others had outlandish tales of Sofia equipping workers with technology and sending them into different universes. Whatever happened that Halloween, it was muddled to say the least.

One story proclaimed that Sofia did indeed have people taken from the streets, those that society wouldn't miss or those that no one would look for them in a massive search. The story continued with the implications with some details from other stories used, that Sofia implicitly had people taken from other universes, since if she had people continuously taken from this universe, there would be a great chance that she would be caught. As this story went, she had the people collected taken through an infamous procedure known to man, one that tops all of all inhuman procedures. The story dubbed this procedure as the Conversion and spoke in great detail about it.

It was a lengthy process, with horrifying steps and the like that would make most ill to their stomachs. There was a handbook that was produced that detailed every process in the Conversion, each step more gruesome than the last, and even the most hardened of people couldn't help but turn away at the sight. What was included in the handbook was also something of questionable ethics, a guide to selecting a person, a random person that no one would bother to look for, as the handbook detailed.

It was a long agonizing hours before the Conversion concluded. Out of the fifteen subjects that made it through the Conversion, only five survived. In a fashion that could be considered a cruel joke depending on who was asked, Sofia ordered the surviving subjects to be garbed as Italian plague doctors, bronze masks and all. These five subjects were named in ordinance of activation: Alpha, Beta, Gamma, Delta, and Epsilon. These five made up the Alpha Series and was promising with the sheer brutality they could inflict on any Cybermen or other.

Of course, that story was seen as child's play, nothing more. Then there was another story, titled, "The Red Letter Day"

It heavily borrowed from other stories and formulated its own version of the tale.

Unfortunately, Sofia had no idea what she had wrought with her Subject Alpha series. On the Red Letter Day, the Subjects begun to act frenzied, not obeying the Keepers, the Guards were no match, and Warden Ryan had been slain by Subject Alpha itself. The Alpha Series' left countless dead and several injured before they disappeared, never to be found or heard of again.

After the Red Letter Day, in a fit of rage and fear, the Corporation fired everyone who was still alive and shelved the project permanently. The Compound was abandoned shortly after the Corporation destroyed much of the work leftover from the disbandment and has remained in the darkness of the Pacific since.

In the present, Hal Corporation dissolved after it came to light what happened, though details were heavily wiped clean or otherwise destroyed. When asked about Sofia Lamb and several others' disappearance, the former chairmen refused to answer. On the whereabouts of the Compound, again, the former chairmen refused to disclose the location of the Compound or that if it even existed, leading countless to be jailed for war crimes.

At least one chairman gave some details about Sofia Lamb; in return, he'd get a lighter sentence. Sofia Lamb had taken her daughter, Emma, with her after the Corporation fired her and the others. Parliament didn't initially believe him, because it never found details about Sofia being pregnant or even married. The chairman explained that Sofia was estranged from her ex-husband and had broken off all contacts with him, hiding from him her pregnancy. She was only a few months pregnant when she disappeared.

Detectives were dispatched and confirmed the chairman's story. Sofia Lamb had been married at one point, to a popular politician no less. Their marriage never lasted more than a few years before Sofia joined the Corporation, divorcing literary the month before she departed. The fact she was pregnant at the time of her disappearance, only made the implications worse.

In the wake of the Corporation's trial, various tapes had been discovered. Pre-recordings of several members of the science team that once worked in the Compound. Amongst them was Sofia Lamb herself:

"Hello and good evening. Today marks a very special day, the day that the Alpha Series has been a success. For those that worry about what these were, do remember that anyone would do anything for the sake of their fellow man. I have been told there had been concerns about morality amongst my team, I shall inform you same. Life is without meaning if no sacrifices made."

Various recordings had been transcribed, but several others had been corrupted to an extent. All made by those who worked in the Compound at some point. Majority of recordings were never paired with a proper face and no one had been able to track down who made them. The content of these recordings varied, though majority seemed to be journal entries, announcements, and with occasional motivational recordings on Sofia's part.

Since, no one has ever had concrete clues as to what happened to Sofia and the rest of the scientists. This is where "The Red Letter Day" ended, with an ambiguous ending.

It became a sort of myth; the kind molded into science fiction novels and passed off as original. Stories of what might've happened were rampant, with twists and turns that are expected in a story. In fact, some people even wrote their own version of events into fanfictions between their favorite characters and the like online on websites dedicated to that sort of thing. The most popular adaption of the story was a well-known video game franchise, though due to the scarcity of details, names and like had to be changed and the franchise's story had to be changed in places to avoid controversy.

Movies and even television shows had even made arcs revolving around the story. The most popular of both have been both in the science fiction category. For movies, the more popular adaption had been adored and fawned upon by fans for close to twenty years, expecting a sequel sometime June or July of the next year. As for television series, a well-known TV series from Great Britain had made it as an arc episode with three parts during its early years when the case was fresh.

At this point, no one will ever really know the truth. The final member of the chairmen behind the Corporation had recently died of illness while serving his twenty-to-life sentencing in his homeland of America, even then he still refused to tell anyone what really happened in the Corporation or if the Compound ever existed. The former detectives who were originally put on the case had retired elsewhere and had no interest in digging it up ever again.

Whatever happened within the Compound, will never be truly known to the public. There would be no way for anyone to enter it now, the Corporation had since fused the doors and entryways shut, so no one in a sub or other could pass through the canals built to transport subs or the like to a holding area.

It didn't stop the Doctor from trying his hardest from looking, however.

A year ago, the Doctor and his cohorts encountered the late Plague Doctor. The Plague Doctor had been traversing between two different universes, one where the great detective Sherlock Holmes and his companion, John Watson, resided in, and another where UNIT was prominent.

The Plague Doctor spoke cryptically about the Corporation and Sofia Lamb, but was killed on orders handed down to UNIT before he said anything more. His remains had been cremated and the Doctor still seething over the death. The Doctor had been looking into the Corporation and what became of Sofia Lamb, rather obsessively. In a year, Clara had left for elsewhere, leaving the Doctor alone in his quest.

The Doctor had been scouring the different universes, looking for the fabled Compound that had been on his mind since he came across stories about it. Most of the time, he found only adaptions of the story, nothing more. Other time, no one knew what he was talking about.

It would be only weeks before the Doctor came across a cryptic letter, it took time for the TARDIS to transcribe but when it finished, the Doctor stared at it. It was a pleading letter, written from someone trapped in the Compound, begging for someone to break them out. Sofia Lamb had gone mad, the letter stated, and she rather everyone die than for anyone to escape the Compound.

Before the Doctor jumped on the chance to locate the Compound, he realized he did in fact need someone or two to help him. While he was the Doctor, he himself needed help here and there. So, the Doctor called Sherlock up on the mobile. Sherlock agreed and the Doctor asked about John. John had recently become a father and had taken a break from chasing crime with Sherlock to raise his newborn. It was just the Doctor and Sherlock this time.

Sherlock agreed to be picked up at his flat at a specific time. The Doctor then prepared for the journey ahead.

The Doctor gritted his teeth as he went around the TARDIS. He stomped his heavy feet as he went about, muttering under his breathe. In his mind, it was justified. The Doctor continued this, fuming at the top of his peppered hair as he went around claiming books and tossing them aside. Suffice to say, the Doctor was ready for the confrontation ahead.

He managed to stop himself once he saw the time. It was precisely noon and it meant that Sherlock would be expecting him. The Doctor cleared his throat and fixed up his bowtie. He ran a hand through his hair and lightly touched his brows before he walked toward the control panel and began to set the dials. The TARDIS would arrive in the den of the flat, in the center near the back wall, far from anyone's sight and then some.

Once the Doctor was done, he flicked the switch and the TARDIS began to hum lightly.