Until now, information on the follow-up to Myst, the 1993 groundbreaking interactive drama that finally gave 2.5 million people a reason to use their home computers, has been harder to find than the code to the Mazerunner in the original game. (One fan even set up a Web site to sift through rumors of the new game’s arrival.) But the creators of the tale, brothers Rand and Robyn Miller, have granted NEWSWEEK a peek at the work, which is still deeper in progress than the Miller sibs and their anxious distributor, Broderbund, had hoped. The targeted release date is not until next summer. So much for the bad news. The happier revelation is that the multidisc sequel, entitled Riven, just may top its predecessor in visual intensity, gameplay, plot, characterization and–hooray–coherence.

Did we utter the S word? Sorry. ““We’re not working on the sequel,’’ insists 37-year-old Rand Miller, the brother who monitors the technology side of affairs. ““We’re working on the next big thing. We want to be the thing that tops Myst.’’ Brother Robyn, 30, an artist and musician, affirms that Riven, though its story line picks up on the Mystian saga, will be seen as a breakthrough in and of itself. ““We have a world that is so much more believable than Myst was.’’ Whether it’s the pod-shaped buildings that house some of Riven’s inhabitants or an exquisitely rendered wood-grained texture on a nightstand in a character’s bedroom, he says, ““you have a feeling that this is a real place. All of it ends up looking more varied and real than Myst.''

In fact, the mammoth, two-year modeling effort on Riven will make the Myst graphics–much heralded for their arty photorealism–look like rough drafts of reality. Where Myst, for example, featured a mountain slope with one kind of rock, a Riven mountain slope has topsoil as well as rock. Even fans might not remember, but there were no clouds in Myst, and the water didn’t move. In Riven there are clouds, and the water not only moves but shimmers. All of this requires the kind of computer power previously exploited only by military operations, major universities and George Lucas. Cyan, the Miller brothers’ company in Spokane, Wash., has 13 pricey Silicon Graphics workstations cranking out 3-D computer models for thousands of objects, ““down to the container that holds the juice that goes in Gehn’s pipe,’’ says Rand. (Gehn is one of Riven’s main characters.) The software used to render these objects is made by SoftImage, the company that did ““Jurassic Park’s’’ dinosaurs. And the SoftImage people claim that in terms of techno-complexity, the Miller brothers’ effort makes ““Jurassic’’ look puny.

While the graphics are eating up much of the costly production effort (an estimated $5 million as opposed to $600,000 for Myst), the brothers are equally proud of Riven’s spiffed-up plot and character development. ““There really wasn’t much of a story’’ in Myst, admits Robyn. But Myst veterans won’t be surprised when they learn that Riven’s improved plot will be revealed only by exploration. ““You’ll get it as you go around; it’s an a-ha experience,’’ he adds.

This much can be revealed: Riven begins where Myst ends. In case you haven’t spent the estimated 40 hours of gameplay required to get to that point (or consulted a cheat book to get there), that’s where you learn that Atrus, the world-making bibliophile who lived on Myst Island, is trying to free his wife, Catherine, who has apparently been imprisoned in some other world, one called Riven. It turns out that Atrus’s father, Gehn, is also trapped there, an interesting development since Gehn himself created that world by ““writing’’ it in one of his magic books. The player’s task is to go to Riven and help Atrus, particularly by freeing his spouse.

But just as was the case with Myst, the real pleasure of Riven will be the ability to wander a magical, yet realistically rendered landscape, trying to solve vexing puzzles in order to discover more. (This approach, a strong contrast to carnage-laden games like Doom, has helped Myst win a female audience; as much as 40 percent of Mysters were women.) In fact, the Millers want to make it easier to browse. ““You can get lost in this real world,’’ promises Rand, who also vows that the puzzles will be more closely related to the plot. Another difference will be that with Riven, the quest won’t be as solitary. ““Myst had a lonely feel,’’ says Rand. There were only fleeting appearances by a few characters, played by the brothers themselves and filmed in a basement in four days. Riven, by contrast, will use nearly 70 live-action sequences including professional actors, such as a 71-year-old Shakespearean thespian for the Gehn role, and a horde of extras, costumed by the Seattle Opera Company, who play villagers, guards and the rebel woman in the scene described above, filmed last week in San Francisco.

Riven explorers will also encounter some strange creatures. ““They won’t be scary in a monster sense but perhaps like a killer whale,’’ explains Richard Vander Wende, a computer artist hired by the Millers after working on Disney’s ““Aladdin.’’ Two of the creatures have been dubbed Whark and Ytram at Cyan, though their Riven names are yet to be determined. The idea, says Rand, was to try to come up with a creature that you could find in National Geographic. ““But when you look at it you see weird textures and tusks in places you’ve never seen them before.''

It’s the prospect of creating such novelty that keeps the Millers going, though surely after their megablockbuster they could have gone in other directions. Hollywood offers abounded, and there was always the prospect of early retirement on the mammoth sales of Myst, related paraphernalia (everything from posters to duffel bags) and royalties on a fat book deal for Myst-based novels. Instead, the offspring of a local minister stayed home, retained their modest homes and cars, and built up Cyan, their privately held company. ““I wouldn’t have been content to rest on my laurels after that product,’’ says Robyn. The stakes in following a $100 million blockbuster are very high, and some analysts think a repeat is unlikely. On the other hand, Broderbund, a company in need of another hit, indicates that 85 percent of Myst buyers will snap up the successor.

The mood at the Miller brothers’ company is collegial though intense. Though Cyan is headquartered in a suburban office building, there are Myst-like touches: a moat, a planetarium-like ceiling in the basement art department and innumerable scuff marks on the conference-room windows, a legacy of Frisbees hurled inaccurately in frequent matches of ““disc golf.’’ Small distractions to deflect the pressure of following up a landmark in gaming that, to the astonishment and delight of the Millers, has yet to be surpassed. ““We always expected that someone would leapfrog Myst before we did,’’ says Rand. Now it appears that the great leap will come next summer, with Riven.