The nuclear-disablement team went first but found no sign that the containers held anything radioactive. They then passed the job to the chemical-warfare specialists and bomb-disposal techs. External tests on the containers were inconclusive, the officer involved said, so the soldiers took up the unenviable task of breaching the vessels to find out what exactly was inside. Wearing protective suits and breathing apparatuses, they put the first lead-lined container inside an airtight glove box within what the officer called a ‘‘secure, reinforced’’ shipping container, and then monitored it from afar by video as the spinning bit from a remote-controlled power drill plunged through the container’s soft wall. Out spilled ordinary mercury, the old standby of red-mercury scams. The second container was empty. In all, the officer said, the mercury amounted to ‘‘about a quarter or half cup.’’

The American soldiers quietly packed up and flew home. Their mission is memorialized in the Army’s classified records with a title — Operation Chimera — that members of the American bomb-disposal community said suggested a certain sense of humor about the whole affair. How the Europeans had been deceived is not publicly known. (One American familiar with the events said a European special-forces team had been lured into a bad buy.) On that matter, the American military declined to comment.

This was hardly the worst of the hoax’s real-world effects. In southern Africa, it has cost lives. According to a regional and especially cruel variation of the legend, the substance is found in conventional military munitions, particularly land mines, there to be claimed by anyone daring enough to take them apart and extract the goods. Tom Dibb, the program manager in Zimbabwe for the Halo Trust, a private mine-clearing organization, said he and the local authorities have documented people being killed in explosions while hunched over land mines or mortar bombs with hand tools.

In the bloodiest incident, in 2013, six people were killed near Harare, Zimbabwe’s capital, by a blast in the home of a faith healer. One victim was an infant. Dibb spoke with the police and said ‘‘they were pretty convinced that it was a tank mine being taken apart for red mercury.’’ In another case, which Dibb examined himself, two men were killed and another wounded as they tried harvesting land mines for red-mercury extraction from a minefield. The most recent death that the Halo Trust investigated occurred on Nov. 1, Dibb said, when a 22-year-old man, Godknows Katchekwama, was killed while trying to dismantle and remove red mercury from an R2M2, a South African antipersonnel land mine about the size of a tuna can.

The explosion outside Harare prompted Michael P. Moore, who manages the Landmines in Africa website, to start a second site, the Campaign Against Red Mercury, which documents hoaxes and urges people not to believe them. Moore said he tried tracing how the meme leapt from sewing machines to explosive devices but could not figure it out. Public-education campaigns were needed, he said, because ‘‘it’s enough of a pervasive myth that it’s not going to go away anytime soon. And people are dying.’’

The Crocodile kept inquiring about red mercury for more than a year, Abu Omar said, pressing for results. He reached out one last time on WhatsApp in June 2015. At the time, Kurds were attacking the Islamic State in Tal Abyad, and the commander also sought what he called ‘‘thermal panels’’ to deceive the weapons-guidance systems on American warplanes. But by November of this year, Abu Omar was still empty-handed. By then Tal Abyad had fallen to the Kurds, and the Crocodile had gone silent, leaving the quest without a sponsor for now.

Abu Omar had kept busy with other work; he said he had recently delivered 23 commercial drones to the jihadists. He remained a storehouse of red-mercury yarns. Word was that the Kurdish fighting groups opposing the Islamic State had been buying up the stuff. ‘‘People I know sold it to Kurds three times,’’ he said. And eight red-mercury warheads had been found in the Aleppo countryside, too. The story was similar to one from Reyhanli, another Turkish border city, where smugglers insisted that rebels in Idlib had overrun a military checkpoint and captured a few grams of red mercury. This material was said to be available for sale, although no one who said this could arrange to see it. It led to an obvious question: If Syria’s military possessed red-mercury weapons, why hadn’t it used them? Why would an imperiled force with a well-documented disregard for restraint forgo uncorking such a weapon as its garrisons fell?