For Mac and Muff Graham, the sea had become part of their lives. He was 43, a retired naval officer from Bridgeport, Conn. She was 40, a sailor's wife who'd become a sailor herself. Married in 1961, they took a round-the-world honeymoon cruise on his immaculate 38-foot oceangoing ketch Sea Wind. Afterward, they chose a close-to-the-sea vagabond lifestyle, based out of San Diego, making ends meet with Mac's modest inheritance, working at odd jobs and living simply on the boat. Both were warm, unassuming, outgoing people, well liked by other yachtsmen. "Muff was the homebody type, not as adventurous as Mac," recalls a friend, "but she went along with her man."

Nevertheless, Mrs. Graham had a sense of foreboding this spring when Mac outfitted Sea Wind for an extended cruise to desolate Palmyra Island, one of a cluster of low-lying atolls about 1,000 miles south of Honolulu. "She didn't want to go," recalls her mother, Mrs. Rose King of San Diego. "She felt something was going to happen."

Remote though the island was, the Grahams had been preceded there by a pair of scruffy social dropouts: Stephanie Stearns, 28, and Buck Duane Walker, about 36, a tattooed drifter. Both had previously been arrested in Hawaii on drug charges, and their very presence on the atoll made problems. Their boat was battered and poorly equipped, and they hadn't brought enough food. The Grahams and a few other yachtsmen who visited the island gave them provisions, but Stearns and Walker were rarely agreeable. Even their dogs were unpleasant. "They let them run wild, and the dogs bit just about everyone," recalls the Grahams' friend Ed Pollock, who anchored three weeks at Palmyra. "They believed in doing their own thing, and if you didn't like it, too bad." Eventually, Pollock and the other visitors put to sea again, leaving the Grahams alone with Stearns and Walker.

By prearrangement, Mac continued to radio Hawaii twice weekly, speaking with ham operator Curt Shoemaker. On August 28, he spoke with Shoemaker for the last time. Shoemaker waited four weeks, hoping the Grahams would show up in Hawaii. When they didn't, he notified the Coast Guard. A pilot overflying Palmyra reported ominously that he saw no sign of either the Grahams or of Stearns and Walker. The Coast Guard put out an alert, but it wasn't until last month that part of the mystery began to unravel.

Taking a walk on the docks in Honolulu's Ala Wai yacht harbor, an off-duty Coast Guard officer noticed two dogs on board a freshly painted, unnumbered ketch. Although the name had been painted over, the boat was the two-masted Sea Wind. When Coast Guardsmen and FBI agents closed in, Stearns tried to flee, but was captured when she stopped for one of her dogs. Walker escaped, but was arrested later. Both were charged with stealing the Sea Wind and $400 that was found on board. The Coast Guard conducted a 36-hour land, sea and air search around Palmyra, but found only the Grahams' campsite, deserted but intact. Sharks circled lazily in the blue lagoon.

Back in Honolulu, Stearns claimed the Grahams had invited her and Walker aboard the Sea Wind for dinner, then had gone fishing and never returned. The next morning, she said, she and her boyfriend found the Grahams' dinghy capsized in the shallows near the beach. After a search that took more than 11 days, she continued, they sailed away on the Sea Wind themselves. "Mac's last words to us were, 'Make yourselves at home,' " Stearns insisted. "That's what we did—we made the boat our home. People who aren't alive," she added later, "can't own things."

Friends and relatives of the Grahams held a memorial service at sea recently, convinced that they are dead. The Sea Wind's dinghy was almost impossible to capsize, they maintained, and Mac and Muff were excellent swimmers. Moreover, friends insisted, the Grahams would never have allowed Stearns and Walker aboard the Sea Wind in their absence. "Mac and Muff were open, friendly, hospitable people," explained one. "But that boat was Mac's life."