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“See ya, Mr. Mathematician!”
These words could hardly be called a promise, but maybe that was why William let his guard down. They were nothing more than a casual pleasantry, the sort of thing people say all the time without truly meaning it.
Ah, perhaps that was the difference.
Sherlock was intrigued, that much should’ve been obvious to anyone paying attention. He’d like to see William again, even if only to satisfy his curiosity and nothing else.
But William, by then, already had a role for Sherlock in his plans. Their unexpected meeting on the Noahtic was a stroke of luck. Someone who could see through William’s schemes—and stop them when necessary—appeared in his path right when he needed it.
And so they would meet again, William would make sure of it. And somehow, Sherlock’s casual “See ya” felt like a confirmation that he would be a part of William’s game, whether he knew it or not.
That’s how it all began.
*
Was the meeting on the train a coincidence? Only William knew the full answer, and he would keep it that way.
Let the team think it was just another test for Sherlock Holmes. Maybe they wouldn’t realize that, just like in Hope’s case, it shouldn’t require William’s direct participation. That part was a small indulgence, but who wouldn’t want to see that brilliant mind at work up close again?
It was then that Sherlock did something unexpected: he drew a promise from William.
A dinner together, someday.
The concept was absurd—a criminal and the man destined to pursue him, dining together as if they belonged to the same world. As if such a future could exist.
And yet, instead of deflecting, William found himself agreeing. His reply was dangerously close to being sincere, and he quickly turned away to leave before Sherlock could try to decode it.
A promise for a promise. At least that seemed fitting.
*
Sherlock invoked that promise not long after.
Was it only a jest? Or had Sherlock sensed something genuine hidden beneath William’s answer that day on the train?
William expected Sherlock to test him after hearing the Lord of Crime’s voice, but he had never imagined it would happen in his own classroom. Sherlock Holmes with a mathematics exam in his hand, imagine that! It was such a surprising view William’s mouth fell open in quiet surprise against his will. Catching William off-guard seemed to be Sherlock’s special skill.
And against all reason, the day became an enjoyable one.
It was arguably the most self-indulgent thing he had ever done. There was a dangerous thrill in walking across the campus in Sherlock’s company so casually, free from the watchful eyes of his team and the expectations that clung to William wherever he went. A guilty pleasure, a stolen a taste of the forbidden fruit.
Of course, Sherlock was observing him throughout it all. William could feel it in every curious glance he threw him when he thought William wasn’t looking. He was searching for cracks and inconsistencies, for anything that might confirm his suspicions, but William would be disappointed in him if he didn’t.
Luckily, there was no risk on the university grounds. No evidence to uncover, no trail for Sherlock to follow. Here, William was simply a mathematics professor. A genius in his field, but an ordinary person beyond that.
Only one moment soured the day. Sherlock presented his psychological portrait of the Lord of Crime, but then claimed he would lay his life for this case if he had to. All to bring the Lord of Crime to justice.
William’s smile nearly faltered.
That would not do.
He wanted, suddenly and irrationally, to make Sherlock promise otherwise. To demand that he survives, that he doesn’t throw his life away in pursuit of the case William himself assigned him.
But such a plea would have been far too revealing. They were still, in many ways, only strangers. They’ve barely met a handful of times. It wasn’t enough to even call them friends.
So William settled for the next best thing—once more a promise to see each other again.
For now, that would be enough.
*
Events progressed fast after that.
There was no time for idle meetings anymore, no time for silly promises to meet again. William’s mind sharpened to see only the ultimate goal and nothing—no one—would stop him now.
Milverton’s little game was a perfect excuse to set things in motion, and so their next meeting came with guns drawn, standing shoulder to shoulder against a common enemy even as they remained enemies themselves. How ironic.
It was there that Sherlock made the greatest promise of all.
Catch me if you can, Sherlock.
I will. I swear I will.
The certainty in Sherlock’s voice struck William deep.
Because if he could make a promise like that without any doubt, then surely he would accept the final request as well. The most important one.
Will you finish the story of Sherlock Holmes and the Lord of Crime?
Of course.
Close, closer. Not long now until the end. Every promise carried them nearer to the finale William had planned long ago.
Sherlock Holmes would keep his promises, wouldn’t he?
The play is over. Let me bring down the curtain.
No.
William faltered.
How could he refuse now, after all the promises he’d made?
Let me go.
No.
Something was unraveling. The script was breaking apart in his hands.
Be the one to make it back alive.
No.
Very well. There was no use for promises anymore. Sherlock Holmes had played his part, and only the river below William’s feet, black and endless, separated him from the conclusion he had sought for so long. He could do this on his own now.
He let go.
For a brief moment, there was only weightlessness.
Then—
Finally, I caught you.
Arms closed around him with desperate force.
How? Why?
Ah. William understood at last.
Sherlock Holmes really did keep his promises.
Liam, let’s live. Both of us. Together.
Wind howled in his ears, but he could hear Sherlock’s words with perfect clarity.
He returned Sherlock’s grip, a promise of his own.
*
Be by my side to light the fire within my heart.
Be my lighthouse through the night.
Billy huffed under his breath. He had heard those words once before.
Through the blur of tears, he could barely make out the exchange of rings, but he didn’t need to see clearly to know this much:
Sherlock Holmes and William James Moriarty had always kept their promises.
They would be alright.