Per 
Let's start… here.
In Yorkshire. 1793. Or was it '94? Time is, at times, rather difficult. Yes, 1794, in August. A dry summer sandwiched between two terrible winters.
A crow repeatedly tapped a crack in a rock wall with its beak, like a thrush that had lost its snail. Occasionally it would stop, turn its head to the side, and stare inside, and then begin tapping again.
Presently, a hand, or something very like a hand, pushed an envelope through. It was properly marked, with postage and address. On the lower right corner was a date.
The crow took the letter in its beak and flew off, wheeling and coursing over the forest, as though looking for something.
When it had flown nearly ten miles from the rock face, it suddenly stiffened and dropped out of the sky, landing on the face of a coachman driving one of His Majesty's mail coaches.
The driver brought the coach to a halt, flinging the crow from his face and cursing the entire family of crows, ravens and, for good measure, jackdaws. It took him several minutes to compose himself. He never noticed the envelope that fluttered down from the sky, through the window of the coach, and in among the mailbags.
Finally, he got the horses moving again and heaved off. He never noticed the crow hopping out of the bushes, nor heard it caw indignantly before it took off in flight again.
Because the coach was late, it arrived at a certain crossroads about fifteen minutes later than it otherwise would have. Unfortunately, the welcoming committee there was rather patient and was still waiting.
"Stand and deliver," said a man standing in the middle of the road. He held a sabre in his hand and wore a dandy's clothing.
"I'll run you down!" the coachman said, shaking the reins. He reached for the cudgel he kept for such occasions, in case the highwayman thought to climb up after him.
He was so focused on the man in front, that he hardly heard the thump as another man dropped from the trees beside him. He thrust a knife into the far side of the coachman's neck, careful to keep the spray away from him.
"Oh, well struck sir!" the man in the crossroads said.
The other man grunted. "Just help me shift him into the bushes."
There is this to know about the two men. One was short and rough, the other tall and handsome. One was good with numbers, the other with words. One was cunning, the other clever. But the most important details are these: One was nasty, and the other was awful.
The two began the work of disposing of the body. However, they had scarcely cleared the coachman from his seat when they heard the thundering of hooves.
"Damn it all, it's the army!" one whispered.
"Then don't stand blinking, run!" the other said.
They tore through the woods, crossing streams, running through brambles, and finally reaching the relative safety of an empty barn.
"I think it might be time to consider a career change, old man."
"I got a cousin in London," the other said. "'E's a fence. Might have work for us."
"Better than nothing, at least to start. We'll head out once the heat's died down and the scratches healed."
But this isn't a story of two men. Not yet, anyway. This is the story of the letter.
Back at the mail coach, the men in red coats left two men to guard it. Eventually another coachman was procured, and the mail made the rest of its journey to London. The letter was tucked safely in with its fellows, and was duly delivered to the address it bore, one Helvington and Sons, Solicitors.
There were no sons, but Mr. Helvington was, if nothing else, an optimist. He was also dependable.
Helvington would provide any service suitable to a solicitor, no matter how inane or odd, so long as it wasn't improper. That is, he would never be party to murder, or theft, or even evasion of taxes. But if you needed, say, three acorns dropped into a certain well in Cornwall on the Equinox, his only question would be whether the species of oak for the acorns mattered. And it would happen, good as clockwork, or better. Helvington didn't need winding.
The letter was taken, placed in a certain folder in his office. There were a number of other letters, some of them very old, some of them nearly as new as this one, and all with dates scrawled on them. It didn't matter to Mr. Helvington that some of these dates ranged from five years hence to centuries later. It didn't matter that the address he had been told to deliver to didn't exist quite yet.
What mattered was that he had been paid to provide a service, and he would provide it, come hell or highwater. So long as that address existed by the time the first date arrived, the letter would be delivered. He would not tamper with the letters, nor would he consider delivering them any earlier or later than the dates provided.
When the time came to deliver the letters, they went to a small packaging firm that had just started up. The firm grew into a private auction house, and then into a club of sorts that catered to the very rich. It was all the same to Mr. Helvington. It only changed the office to which he passed on the letters.
Years passed by, but Mr. Helvington didn't. No one really remarked on it. Even he scarcely seemed to notice. Staff passed through, clerk after clerk, but Mr. Helvington remained, seeing new clients, writing up wills and contracts, and making sure the "particular assignments" were completed. Typewriters replaced inkwells, and computers replaced typewriters, but Mr. Helvington remained. Only his staff seemed to notice anything was unusual, but they didn't dare to ask about it.
One year, the building burnt out, but his office remained untouched. He was paid in more than money for those special services.
Finally, on a spring day in 2016, more than two hundred years later, the date on the envelope came up. He carefully removed it from the folder and gave it to a clerk, with the usual instructions to take it over immediately and not to tamper with it.
There were rumors among the staff that terrible things awaited any clerk or intern who made the mistake of breaking client confidentiality. Disappearances, black hoods pulled over heads, garrotes… All absolute nonsense, of course, the product of overworked imaginations. Helvington would simply sack them.
What the clients chose to do, of course, was none of his concern.
The letter was, therefore, duly taken over to a discreet office with a small, tasteful plate out front and handed to a secretary. It was then taken to a man sitting at a desk. He was tall and handsome, clever, good with words, and awful.
He carefully opened the letter with a pen knife, and slid out the paper. He blanched when he read the only two words on the letter.
RESTORE CARTER.
