On a white restaurant tablecloth in San Francisco, under the glow of a stained-glass dome ceiling with images of laurels, fleur-de-lis, and a ship, rested a portion of metal the size of a shallot. Around it, three men were having lunch one day in the summer of 2018. Jacques Vallée, a French information scientist, was explaining to Max Platzer, editor of a top aeronautics journal, how the metal had come into his possession. The story wound back more than four decades, he said serenely, to an unexplained episode in Council Bluffs, Iowa.

On a cold Saturday night in late 1977, firefighters and police had responded to calls about a roundish, reddish object with blinking lights that hovered above the treetops in a public park, then dumped a bright mass onto the ground. When investigators arrived on the scene, they found a 4- by 6-foot puddle of metal, molten like lava, that lit the surrounding grass on fire before cooling. All told, 11 people from four separate groups gave similar accounts of the incident.

A piece of this puddle was now sitting a few inches from Platzer’s plate. The mystery, Vallée said, was where the material came from originally. Metallurgical analyses at the time showed that it consisted mostly of iron, with traces of carbon, titanium, and other elements—basically, steel alloy scrambled to what looked like cast iron. It couldn’t be satellite debris or equipment falling from a plane, Vallée pointed out; those wouldn’t have gotten hot enough to melt, and they would have cratered the ground. Nor, for the same reasons, could it be a meteorite. And there wasn’t enough nickel for a meteorite anyway.

Could a hoaxer have poured the metal in place? Unlikely, Vallée said. That would have required an industrial furnace, plus some way of transporting the molten material. A canvassing of the local metal businesses had turned up nothing. Thermite was a possibility; it burns hot enough to melt steel and wouldn’t produce a crater. But to create the cast-iron-like material that Platzer saw before him, the perpetrator would have had to douse the puddle in water, and the water would have frozen, and there was no ice on the scene.

Vallée thought the metal deserved a look with the latest technology. This was where the third man at the table came in.

Garry Nolan, now eating a burger, was a pathology professor at Stanford University School of Medicine. His specialty was analyzing cells, especially cancer and immune cells, but some of his techniques worked on inorganic matter too. His equipment could, for instance, parse a metal sample at the atomic level, telling you not only which elements it contained but also which variants, or isotopes, of those elements, and where inside the sample they occurred. This, in turn, could offer clues as to where the material was manufactured—on Earth? elsewhere?—and possibly even its purpose.

Platzer was not the sort you’d expect to attend a lunch about UFOs. He made his bones working on the Saturn V rocket, the launch vehicle that conveyed humans to the moon, and he taught for three decades at the Naval Postgraduate School. But he had made inquiries into these two men. Nolan’s reputation was “impeccable,” he told me later, and Vallée’s was “outstanding.”

Vallée, who is 82 now, has celestite eyes, a strong nose, and a head of sterling hair that seems to riff on tinfoil hats. Beneath the rare hair is a rarer mind. His recollections from a six-decade career as a scientist and technologist include helping NASA map Mars; creating the first electronic database for heart-transplant patients; working on Arpanet, the internet’s ancestor; developing networking software that was adopted by the British Library, the US National Security Agency, and 72 nuclear power plants around the world; and guiding more than a hundred million dollars in high tech investment as a venture capitalist.