On July 11, 1897, three Swedes—Salomon August Andrée, Nils Strindberg and Knut Frænkel—set off on one of the most ambitious Arctic expeditions of all time: a bid to fly over the North Pole in a hot air balloon called “The Eagle.”

It did not end well.

Their fate remained shrouded in mystery for 33 years, until August 1930. That’s when a group of Norwegian walrus hunters on the island of Kvitoya—a 250-square-mile ice-covered rock, lying in the far northeast of the Arctic Svalbard archipelago—stumbled on a remarkable find.

Frozen beneath a mound of snow, the hunters uncovered remnants of a small boat; nearby, they discovered the remains of two men. The following month, a follow-up team came across a third body, as well as a scattered assortment of journals and equipment.

Writing 70 years after the discovery in their book A Fabulous Kingdom: The Exploration of the Arctic, Charles Officer and Jake Page note that those journals made it clear that Andrée and his companions knew as they wrote that their end was near.

“We think that we can well face death, having done what we have done,” Andrée wrote. “Shall we be thought mad?”

The expedition had been the brainchild of Andrée, a Swedish engineer working at the country’s patent office, who had developed a fascination for both hot air ballooning and polar exploration. Having been introduced to ballooning at the 1876 World Fair in Philadelphia, Andrée eventually procured his own balloon in 1893 and undertook several journeys in which prevailing winds carried him to the east across the Baltic Sea.

In 1894, Adolf-Erik Nordenskiold, a fellow Swede and polar explorer who had been the first to sail the Northeast Passage in 1878, asked Andrée what he thought about using a tethered balloon to rise above the ice and look beyond it, writes author Alec Wilkinson in his book about the expedition, The Ice Balloon. Andrée reportedly responded that surely untethering the balloon and flying over the ice would reveal far more.

The following year, Wilkinson writes, Andrée stood before the Royal Geographical Society and presented a plan. To this point, he began, men had attempted to traverse Arctic ice by sailing into it with ships that almost invariably became entombed—and then attempting to haul sledges across its surface. It was time, he said, to consider another option. “I refer,” he said, “to the balloon.”

Andrée argued it would be possible to steer the balloon through a combination of a sail attached to the bag and heavy “drag ropes” that would slow the craft down by dragging through the water or along the surface of the ice. In response to concerns that no balloon could possibly remain inflated for the time it would take to complete his journey, he countered that the voyage would take half as long as people expected, because the 24-hour summer sunlight in the Arctic would enable him to fly and make observations all day and all night.

When General Adolphus Greely, recently returned from his own expedition to northwest Greenland and Ellesmere Island, rose to question the safety of Andrée’s idea, the Swede retorted by pointing out that 18 of Greely’s 25 crew had died.

“I risk three lives in what you call a ‘foolhardy’ attempt, and you risked how many?” he asked rhetorically. “A shipload.”

The audience, a witness reported, stood up and cheered.

Andrée’s first attempt proved a disaster. In 1896, he and two companions he had selected for the voyage set out for Svalbard with the balloon he had bought especially for their expedition, which he dubbed Ornen, or The Eagle. There, they waited for the winds to pick up from the south and carry them aloft and poleward.

As they waited in Svalbard, however, the promised south wind never came, instead blowing hard from the north until Andrée, defeated and deflated, realized they had no option but to pack up and go home. Excoriated in the media and derided as a “fraud” in some quarters, he resolved to return. The following year, armed with funding from Swedish inventor and businessman Alfred Nobel, he did—along with his two crew members, 24-year-old photographer and scientist Strindberg and 26-year-old engineer Frænkel.

On the morning of July 11,1897, Andrée dictated telegrams to Sweden’s King Oscar and the newspaper Aftonbladet, and the balloon left the ground—only to be pulled so far down by the drag ropes, which were each several hundred meters long, that the basket dipped into the water. The friction pulled many of the ropes loose, as Andrée and his companions frantically threw ballast overboard. The balloon rose high—higher than it was supposed to—and soared off into the distance, never to be seen again.

Not until the discovery of the bodies, the journals and Strindberg’s photographs in 1930 were researchers able to piece together the story. The Eagle managed just a little over 10 hours of free flight, followed by more than 40 hours of alternately rising and falling and bumping along the ice, before, weighed down by moisture, it eventually crashed. The men loaded provisions onto sledges and set out for a previously established food depot on the Arctic archipelago of Franz Josef Land.

However, as they marched east, the ice drift kept pulling them west. They were barely making any progress, their clothing was insufficient for the conditions and their sledges were too heavy and rigid. After discarding many of their provisions to lighten their loads, they began shooting polar bears and other wildlife for food. Fatefully, they decided to change direction to the southwest, only to find the sea ice terrain undulating and treacherous. At times, they literally had to crawl on their hands and knees to navigate it; eventually, they made camp on a flat ice floe that drifted toward Kvitoya.

They came ashore on October 3, but within days they were all dead. Frænkel, whose body was half-buried and the last to be found, probably died first. Strindberg’s last diary entry was October 5, after which he presumably became the second to pass away. Andrée penned his final entry on October 7; he was found sitting upright against a rock, journal and rifle at his side.

After their discovery, the bodies were returned to Sweden. A procession carrying their remains into Stockholm was later described as “one of the most solemn and grandiose manifestations of national mourning that has ever occurred in Sweden.” Today, the promontory where they came ashore and were found is known as Andréeneset, where a simple concrete monument acknowledges their final resting place.