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Sherlock had learned many things about William since they started living together. From his poor appetite to his habit of inhaling fragrances he liked, William's quirks were a peculiar mix of endearing and concerning. Sherlock never expected someone could be so sweet and yet so unhealthy at the same time. If he were to list both the good and the bad, he would say William looked absolutely adorable, like a cat, when eating stargazy pie and unbearably irritating when he overthought things to the point his brain forced itself to shut down.
But one thing truly surprised Sherlock and something he had only recently come to realize. When William was under extreme stress or overwhelmed by anxiety, he would sleepwalk.
The first time it happened, Sherlock had assumed William had simply gotten up for a glass of water in the middle of the night. Nothing seemed unusual until William didn't return for some time. When Sherlock went to check, he found William standing motionless in front of the bookshelf, his eyes open but completely vacant. At first, he thought William was just lost in thought, but when he tried to speak to him and got no response, suspicion began to grow.
"Liam?" he called softly, not wanting to startle him.
But there was no reply. William stood like a statue, unmoving. His eyes remained open, blank and his breathing was slower than usual. His body started to lean forward slightly, as if preparing to take another step.
Sherlock gently reached out to stop him, placing a hand on his shoulder, but William didn't react. A strange feeling stirred in his chest. Carefully, he guided William back to the bedroom, holding him by the shoulders and waist. As soon as William's back touched the mattress, his body relaxed, and his eyes closed on their own. He seemed to fall back asleep instantly.
The next morning, when Sherlock brought it up, William had no memory of it.
"I was standing in front of the bookshelf?" William repeated, clearly confused. "I don't remember that. Are you sure I wasn't just talking in my sleep?"
"No," Sherlock shook his head. He was certain it hadn't been a dream. Looking back, the symptoms matched those of sleepwalking. Still, he had never come across such information when investigating the Moriarty family. And judging by William's clueless reaction, perhaps his family had kept this from him.
The conversation ended there, but Sherlock became more observant afterward. He knew William wasn't the type to talk about his emotions especially when he wasn't doing well. But the signs began to show, especially when William was too focused on a mission, pushing himself for days until stress consumed him.
Exactly two weeks after the first incident, Sherlock woke to find William gone. He glanced at the clock, it was 3:17 AM.
He got up and left the bedroom in search of him. Footsteps echoed faintly down the hall. Sherlock followed the sound and, just as he suspected, found William walking slowly toward the kitchen. This time, William opened the cupboard, took out an empty glass, and stood there holding it, doing nothing.
Sherlock approached quietly and touched William's wrist. As expected, there was no response. He took the glass from William's hand and placed it on the table, then gently led him back to the bedroom, careful not to wake him mid-way. It didn't take long, and once William lay down again, his body softened, and he fell back into sleep.
That morning, Sherlock firmly declined a mission request on William's behalf and scolded Billy about the whole thing. William, unaware that the conversation was about him, remained focused on paperwork.
Sherlock began to think more seriously about the issue. His mind drifted back to something he'd studied years ago when he immersed himself in the psychological aspects of human behavior. He wasn't a psychiatrist or a physician, but as a detective, he believed it was essential to understand how people functioned and how they broke.
Parasomnia. A clinical term for unconscious behavior that occurs during sleep. Sleepwalking was one of them. It typically happened during the non-REM phase, when the body was technically asleep but parts of the brain remained active. Sherlock clearly remembered that it was often triggered by chronic stress, prolonged mental fatigue, repressed trauma, or a habitual refusal to process emotion.
And all of it applied to William and he was the perfect storm.
William kept too much inside. He didn't just avoid talking about his emotions, he outright denied them. Whenever possible, he would act as if nothing was wrong, even when it affected his physical condition.
Sherlock knew because he used to be the same.
But now he saw it in someone he loved, and it hurt more than he'd ever imagined.
Sleepwalking wasn't just a strange occurrence. It was a glaring signal that William's mind had reached its threshold and desperately needed release. Sherlock began to understand that this was William's subconscious crying for help.
It made him wonder, was this the first time? Or had it happened before?
And then his thoughts turned to one thing.
The Moriarty family.
They had been a tight-knit group of brothers working to dismantle the cursed class system in England. Their organization was filled with talented, loyal people who helped drive their shared mission. And William had been at the center of it all, both as a sibling and a leader.
Could they have known about this?
The more Sherlock thought about it, the more it made sense. Perhaps, when William was still a teenager, episodes like this had already occurred. And instead of worrying him with the truth, the Moriarty family chose to hide it. Maybe they didn't want William to feel weak. Or maybe it was the only honest indicator of William's mental state, a state that was usually impossible to read. Perhaps they had held onto that truth out of a selfish desire to break through the emotional walls William had built in order to carry their plan to the end.
If that was the case, then Sherlock had to ease the burden and insecurity William still carried. The problem was, William would never say what made him feel unsafe. Even when Sherlock asked directly, he would just shrug, smile faintly, and say he was fine. But Sherlock knew his insecurity didn't come from a single event. He couldn't just sit him down, talk it through, and expect everything to be fixed.
So over the past three years, living side by side, Sherlock had made a silent vow to be a home for William, especially in moments when he missed his family or felt the weight of his own guilt. He hoped that somehow, William would feel the sincerity of that vow and come to understand that with him, there was no need to be afraid.