You mailed the letter, replete with torrid images and mad protestations of undying love, weeks ago, but your beloved's mailbox remains empty -- and one more promising romance is threatening to self-destruct.

What happened?

Your letter died.

Unwittingly, you made a mistake while addressing the thing and your epistle could not be delivered. And now, the passionate missive is in the hands of the 36 staff members of the Mid-Atlantic Dead Letter Office, where this kind of thing happens millions of times a year.

These are the people who intercept packages of machetes on their way to an indecipherable address in Nicaragua. Who feed and care for the survivors of a dwindling school of tropical fish whose water has leaked in transit and washed out the address of their destination. Who redirect lost envelopes intended for the unwitting betrothed, envelopes the Dead Letter people know enclose farewell letters and rejected engagement rings.

Each day, they must find homes for burnt letters, mangled letters, misaddressed letters, unaddressed letters, Chinese-addressed letters, incinerated letters destroyed by firecrackers thrown into mailboxes -- a total of 7 million to 8 million Dead Letters a year, to say nothing of the 300,000 Dead Parcels. (Nationally, 74 million letters -- and 1.1 million parcels -- succumb annually.)

All of which can give you a somewhat pessimistic view of the modern world.

"How does it happen?" asks clerk John McDermott, who has spent 10 years in the Dead Letter Office confronting this insoluble mystery. "You don't know. Doing too much at once, I suppose."

Wedding rings slip off fingers, bankbooks slide from hands, all into the mailbox. Interoffice memos somehow find their way to the Out box and then, whoosh, land in the Dead Letter Office. Stamps are forgotten and return addresses omitted. Letters are stuffed backwards into window envelopes, so the address is not visible ("This is what we call a 'turnaround,' " says the superintendent of the claims and inquiry branch, Barbara Bonaparte. " 'Turnaround' is just our lingo for it").

And then, of course, there are the thieves who throw pocketbooks and wallets, sans cash, into the nearest hiding place, which very often happens to be a mailbox. The plane crashes during which letters are first burnt and then drenched with water. The discontented taxpayers who refuse to put stamps on their federal returns, not realizing the IRS won't accept postage-due mail.

And the children from the seven states and the District of Columbia under this office's jurisdiction who write between 200 and 1,000 hopeful letters a day every day from Thanksgiving to Christmas.

"The Santa Claus mail comes to us, of course," says Bonaparte, "because it's undeliverable as addressed."

It all ends up here, in this cavernous room filled with fluorescent light and table after table of wallets, undeveloped film, stuffed animals, bank certificates, packets of mail-order panty hose, books, credit cards, and letters, letters, letters.

"A lot of people think, 'The Post Office throws my mail out,' " mail clarification manager Jim Elliott says grimly, surveying the landscape. "This is what happens to it."

But don't worry that just anyone will be trying to resuscitate your letter.

"The only people who can open these are certified senior personnel because of the sanctity of this seal," says Elliott, pulling a letter from a box and displaying it, seal-forward, with the reverence of a priest displaying a sacred object.

Once the letter is officially declared dead, it goes to the clerks in the section of the U.S. Postal Service's Philadelphia Claims and Inquiry Branch -- which is affectionately, but unofficially, called the Dead Letter Office. And then they begin the search, attempting to discover where the dead object came from or where it was supposed to go. The seal is broken. In search of any sort of address, they read the letter.

Which raises the question of privacy.

"When we're working, and we come to something interesting, they'll hold it up so everyone can see," says Bonaparte, but she's referring to stray fish or machetes, not the heartfelt outpouring you intended for His or Her eyes only. When it comes to heartfelt outpourings, the lips in Philadelphia are sealed.

For the more experienced employes, it's a matter of boredom. Ask someone like William Nix, who's been with the Postal Service for 30 years and the Dead Letter Office for nine and has probably read it all, if he slows down to savor a particularly lyrical love letter or unusually effusive birthday card, and he tells you, "Not after awhile, after a year," his face a study in disinterested professionalism.

For others, it's a matter of pride.

"I don't read the letters," clerk Linda Washington insists. "I don't. I don't make time for it.

"I get mad," she says, lowering her voice in a way that suggests if you got her outside the massive walls of this Depression-era post office, she'd have tales to tell. "You see people doing it. But the address is usually at the beginning or the end. I put myself in their place . . ."

Then she pauses, pensive, her Dead Letter Office pragmatism returning.

"But if it's that personal, I wouldn't put it in a letter," she says. "And look at it this way -- if they don't want anyone reading it, they wouldn't put the wrong address on it."

Work in Dead Letters and you begin to lose patience with certain aspects of the national psyche.

"All you have to do is come in any time after January 1st," says Elliott. "You'll see our trays. Just 'IRS.' No postage. They write nasty messages on the outside, on the envelope too. 'Taxation without representation!' Things like that. You know how you check that box on the front if you're getting a refund? Even people who are entitled to the refund don't put postage on it."

Denizens of the Dead Letter Office, who manage to return 25 to 30 percent of the letters and packages, have other peeves as well.

*Dishonesty. "Preprinted envelopes," Elliott says wearily, holding up an envelope, the name of a major bank already printed as both destination and return address. "That's the way they try to beat the system. They don't put any postage on. That's fraud. We turn that matter over to the postal inspectors."

*Chutzpah. "You get people calling up saying, 'I've lost $10,000,' " says Nix. "They're just cranks. If you put $10,000 in a mailbox, you sit by that box."

*Youth. "College students, when they clean up to go home, they put 70 pounds in a carton that is made to take 20," says Elliott. "You know college students."

*Lack of gratitude. "They made the mistake," says Nix of the owners of the misbegotten letters and parcels, "but they put it right on us, we're responsible."

*Photography. "These just rip right open," says Elliott, demonstrating on a flimsy envelope used by film developers. "And they don't write their name and address on the film. It's a shame. We've had a lot of wedding pictures. People can't understand how much of this we get. They'll say, 'I'm standing in the church, in the yard.' They just describe it and don't know how many come here."

Even Dead Letter veterans engender Dead Film. But, if you take the time to write your address on the cartridge, you, like Linda Washington, will see the wayward film again.

"I had to laugh," says Washington of the cartridge that wound its way home to her after leaping from its envelope.

Let it be a lesson to you.

A Dead Parcel can be just about anything. A signed Miro' lithograph, insured for $15,000 and damaged during delivery (after the Postal Service insurance on objects has been collected, the Dead Letter Office assumes ownership and auctions the items off. "Essentially," says Elliott, "they become dead."). The first reel of a three-reel "Three Stooges" movie. The last reel of "Prizzi's Honor." A pair of red and white polka-dot sandals. A gold Omega watch. A very large carpet. A belt given as an award to singer Hank Williams Jr., successfully traced and returned.

"It's depressing, because all of these things belong to someone," Bonaparte says sternly. "It means whoever it is, they won't get it. It's very sad, especially with very good things -- not the idea of the expensive things, but something you know has sentimental value."

Like the baby shoes.

"They were gold-plated," says Elliott. "Probably worth a lot. All we had was the date of birth."

And even the Dead Letter Office needs more than that. As John McDermott puts it, remembering one father's futile attempts to track down the pictures of his son's graduation that disappeared on the way to the developer, "They don't all have a happy ending."

But despite the hours spent waiting for waterlogged cinders that were once letters to dry, despite the crank calls, despite the dead fish, people will tell you life among the Dead Letters isn't too bad.

"It's not work," McDermott claims. "I think it's very interesting, because I'm helping people the way I'd like to be helped. It's a joy -- finding money they can't afford to lose. One of my biggest thrills was once finding $800 here. The woman who lost it -- her job was on the line. The money went into the mailbox instead of the bank. She wanted to give me a present. I wouldn't take it anyway, but we're not allowed to."

And, McDermott adds, he has learned a valuable lesson while on the Dead Letter Office payroll.

"I double-check my envelopes," he says, "because of what I go through every day." CAPTION: Pictures 1 and 2, Philadelphia's Dead Letter Office is the repository of millions of misaddressed letters; A wedding band and a $1,000, solid-gold watch found loose in a mailbox. AP