You've got a dream job, running your own cozy secondhand bookstore, complete with Raffles, your caudally challenged cat. It's in Greenwich Village, and your best friend's dog grooming salon is two doors away, and the two of you lunch together and meet for drinks after work.

And you've got another way to make a buck. Every once in a while you put your conscience on the shelf and let yourself into someone else's residence, and you leave with more than you came with. You're a burglar, and you know it's wrong, but you love it.

And you're good at it. You've got two ways to make a living, one larcenous, the other literary and legitimate, and you're good at both of them.

Nice, huh?

Until the 21st Century pulls the rug out from under you. All of a sudden the streets of your city are so overpopulated with security cameras and closed-circuit TV that you have to lock yourself in the bathroom to have an undocumented moment. And locks, which used to provide the recreational pleasure of a moderately challenging crossword puzzle, have become genuinely pickproof.

Meanwhile, internet booksellers have muscled your legit enterprise into obsolescence. The new breed of customers browse your bookshop, find what they're looking for, then whip out their phones and order their books online.

Wonderful. You had two ways to make a living, and neither of them works anymore.

But suppose you keep on supposing, okay?

Suppose you wake up one morning in a world just like the one in which you fell asleep-but with a couple of differences.

The first one you notice doesn't amount to much. The Metrocard in your wallet has somehow changed color and morphed into what seems to be called a SubwayCard. That's puzzling, but you swipe it at the turnstile same as always, and it gets you on the subway, so what difference does it make?

But that's not the only thing that's changed. The Internet's up and running, as robust as ever, but nobody seems to be using it to sell books. Doors are secured not with pickproof electronic gizmos but with good old reliable Rabson locks, the kind you can open with your eyes closed. And what happened to all those security cameras? Where'd they go?

All of a sudden you've got your life back, and your bookshop's packed with eager customers, and how are you gonna find time to steal something?

Well, just suppose one of the world's worst human beings has recently acquired one of the world's most glamorous gems. When the legendary Kloppmann Diamond is up for grabs, what can you possibly do but grab it?

And what could possibly go wrong?