Imagine a world in which hundreds of millions of people do most of their social interacting through computers – working, chatting, sharing and expressing themselves without ever leaving their electronic interface.

Oh, wait. We live in that world, even though today’s reality would have sounded like some science-fiction hallucination only 30 years ago.

OK, then – imagine a world in which people do virtually all of their social interacting through a computer, this time controlling robots that resemble their ideal self-image.

You lay back at home and send your robot clone out to work, to parties, to the grocery store. In everyone else’s eyes, you always look great, you’re thin, you never age and, if you get hit by a bus, your robot dies, not you.

This is the hits-close-to-home premise of “Surrogates,” the surprisingly efficient and smart sci-fi movie starring Bruce Willis.

Based on a graphic novel by Robert Venditti and Brett Weldele, the film inserts a murder-mystery into this environment and then spins it into a grand conspiracy. Yet, the whole thing flashes by in less than an hour and a half, thus avoiding the operatic bloat of most future fables.

Willis plays Greer, an FBI agent in an era where crime has dropped 99 percent and violence is virtually unknown. True, there are enclaves of humans who believe the use of surrogates is wrong, and they march to the song of The Prophet (Ving Rhames), but the vast majority of mankind has gone surrogate and things are peaceful.

This was not, though, the intent of the scientist Canter (James Cromwell) who came up with the technology that made surrogates possible. He was just trying to devise a way in which people confined to wheelchairs or beds might get out and about and live more independently.

Canter has since split from the company, VSI, that turned surrogacy into the norm in everyday life. Now people lie about in their pajamas all day, hair filthy, bodies withered, attached to their computers as their surrogates move through the world.

But then one night, the unthinkable happens. Canter’s son, using one of Canter’s surrogates, is attacked by a living human with a weapon that not only kills the surrogate, but it also radiates back and kills Canter’s flesh-and-blood son.

Soon other surrogate-human murders start popping up, and Greer, along with his partner Peters (Radha Mitchell), start investigating. Soon enough, Greer is caught up in your classic tangled web, his surrogate is destroyed, and he is forced to take to the streets in human form for the first time in years to hunt down the killer.

Some things go a bit too conveniently here – Greer has immediate access to a VSI scientist as well as a top military official – and his investigative style has whiffs of “Dragnet.” But the film moves along so quickly, and the surrogate world look is so eerie, that it matters little.

Dealing with the robot-human interface has become common ground for screenwriters Michael Ferris and John D. Brancato, who penned the last two “Terminator” films, and director Jonathan Mostow certainly picked up some robo-skills helming “Terminator 3: Rise of the Machines.”

Mostow gets in, establishes the premise and the look, cooks up some solid action scenes, lets us know Greer’s human despite it all, and solves the mystery with no grand predictions of impending doom or overlong sidetracks. The swiftness of “Surrogates” is to be admired.

But it’s that basic idea that gets you. It couldn’t happen here, could it? No way. Pass that along on your Facebook page.