"There's this tendency to think the park's beautiful, so it must be benign," says Marsha Erickson, executive director of the Kokee State Park Museum, on the Hawaiian island of Kauai. "People just have no idea how complex this ecosystem is, and how easy it is to disappear."

Indeed, disbelief was the most common reaction when Stephen Reisberg, 34, a doctor at Boston's New England Medical Center, and his wife of less than a year, Jenny Sun-Reisberg, 28, a Harvard doctoral candidate, vanished in September 1990 during a hike in Kokee State Park.

Maybe it shouldn't have come as such as surprise. The local police department's files are peppered with tales of

The disappearance of two people begs the question of foul play and, perhaps, intent: Maybe they never wanted to be found.

tourists lost in Kauai's tangled jungle, of others falling to their deaths, and of unexplained murders, like the 1981 killing of John and Michelle Klein, who may have blundered into a nearby marijuana plantation. This past November, 24-year-old Daniel Marks disappeared during a hike originating from the same trailhead where the Reisbergs' car was found 15 years earlier.

As for the Reisbergs, upon arriving at the 4,000-acre park, they spent nearly an hour in the museum looking at maps of Mount Waialeale, one of the wettest spots on earth, and consulting with museum employee Mark Jeffers. "They were really excited with this idea they had about getting to the summit of the island," recalls Jeffers, the last person known to have seen the couple. "I tried to explain to them that it's not really such a good idea, but they thought they could handle it."

Two weeks went by before local authorities discovered that the Reisbergs were missing and located their rental car at the Puu o Kila lookout. Their fully packed backpacks and camping gear still sat in the car, suggesting that the couple, experienced hikers and campers, had intended nothing more than a short day hike. A massive search that utilized helicopters, tracking dogs, and local hunters turned up a scarf similar to one in Jenny's luggage and a vague report that a hiker may have heard a woman groaning.

David Boynton, a naturalist who helped in the search and acted as guide for Stephen's parents when they came to the island, suggests that they may have tried to hike out along a ridgeline that is visible from where their car was found. It would have offered tremendous views of the Kalalau Valley but also taken them to the brink of a 4,000-foot drop. "There is a fern that grows in thick mats along these ridges," Boynton says, "and I know from personal experience that you can try to push your way through this green layer and wind up stepping off into air."

Still, the simultaneous disappearance of two people begs the question of foul play and, perhaps, intent: Maybe they wanted to disappear. There was a rumor that Stephen was dissatisfied with his work, and island gossips wondered if Jenny, a highly educated Chinese national who had chosen to remain in the U.S., needed to disappear to escape pressure being put on her family by the Chinese government.

"It's one of our cold cases," admits Lieutenant Roy Asher, of the Kauai Police Department. His response to the suggestion that there seem to be an awful lot of strange things going on out there? "Man, you don't know the half of it."