Hi! it shrieks. Notice Me: Basildon Bond envelope, type-written name and address, second-class stamp.
I dump my bags and open it immediately. There is no reason not to. I do not, after all, expect it to contain a threat of death.
I draw out a single sheet of cheap, white photocopy paper.
The heading is shoddily off-centre: WITH LOVE ALL THINGS ARE POSSIBLE.
"This letter has been sent to you for good luck. The original is in New England. It has been around the world nine times. You will receive good luck within four days of receiving this letter, providing you in turn send it out."
The tone is chirpy and certain. Everyone would, after all, like some good luck. A four-day wait seems bearable.
It goes on: "This is no joke, you will receive good luck in the mail. Send NO money as fate has no price. Do not keep this letter. It must leave your hands within 96 hours."
Deadlines, huh? Aren't we getting a bit specific? Do I also detect just the teeniest hint of a whinge creeping in - all those blunt little negatives barked out so defensively? However, "send no money" smacks of integrity. Doesn't it?
The letter fires off examples: "An RAF officer received £70,000." Goodness. National Lottery dreamers, eat your heart out.
"Peter Fry won £40,000 and lost it because he broke the chain. In the Philippines, Buz Meyer lost his wife six days after receiving the letter. However, before her death he received £773,000."
Blimey. Where did Mr Meyer go wrong? Did he forget to put a stamp on? I see a seersucker-suited Buz crossing some hot veranda, celebratory Cinzano clinking in his hand - "Darling, you know that £773,000 we just received in the post ...?" - only to find MrsM stiff and cold on the ottoman. Or did he secretly hate her guts? Was the loss a subtle part of his good luck?
Who is the author of this weird missive, anyway?
The letter jumps to it: "The chain comes from Venezuela and was written by Gordon Lane de Sampa, a missionary from South America. This letter has to make a tour of the world. Mail 20 copies to your friends and associates. After a few days you will get a surprise even if you are not superstitious."
"Even if you are not superstitious!" my partner echoes derisively.
"There's something really unpleasant about it," I say. "Why do people send them?"
He laughs, screws it up and aims a perfect overarm googly into the bin. "Because people like you send them on."
"Oh, come off it," I say. "I wouldn't dream of it." I retrieve it, because I'm intrigued.
It continues breathlessly: "Do note the following. Vivian Vanya received the letter in 1953. He had his secretary make 20 copies and send them out. A few days later, he won a lottery for $2m.
"Franco Rimodi, an office worker, forgot that the letter had to leave his hands within 96 hours and lost his job. Later, he found the letter, mailed 20 copies, and a few days later he found" (surprise, suprise) "a new, better job.
"Eugene Goodyear did not believe the letter and threw it away. Nine days later he died."
"Would you send a chain letter on?" I ask my reliably wacky friend Molly, a psychiatric nurse who sings in a band at weekends.
She shrugs. "I don't know. What harm can it do?"
"Don't you think it's a form of bullying? I find it very threatening to get a letter which tells you what will happen if you don't send it on."
Molly laughs her smoky laugh, "It's all lies. Anyway, most of these people seem to have done all right."
"I don't know why you're giving it so much thought," my partner says. "You're just playing their game."
"I'm not," I tell him hotly. "And I'm not sending it on. No way."
"Makes no difference," he remarks with infuriating cool. "You've let it get to you now. It's the same thing."
Of course it bloody well isn't.
Later, I catch the end of a radio programme about the potential for sex abuse on the Internet. Fast replacing BT's heavy breather, apparently, is the hack who "meets" you via computer and becomes a software pest. Molests you electronically, talks dirty in cyberspace. The first case for assault has been brought to court in Ohio or somewhere.
"Chain letters are the heavy breathers of the postal system," I announce over supper. My partner laughs, of course, but I'm faintly proud of the deduction, because it's true.
They are the charmless desperadoes with the dodgy typewriters, ramming their manipulative rubbish into our (ultimately vulnerable) letterboxes. It's an inadequate nerd's power game, homing in on everyone's (except my partner's) residual superstitionand fear.
And Gordon Lane de Sampa is doubtless right now smoking a fat cigar in some Venezuelan hammock, chortling as his useless brainchild makes its Tour of the World.
And look at me, I'm paralysed by this bit of paper - putty in Gordon's sweaty palm. I won't send the bloody letter on, yet can't bring myself to throw it away.
"Give it to me," Molly laughs eventually. "I can't bear it any longer. Give it to me and I'll send it out."
So I do. And she does. "You're both barking," my partner says.
The following Saturday, Molly is the very first person I know to win £10 in the lottery.