On September 18, 1954 a pair of Australian skin divers emerged from the water off Port Darwin. Kirke Dyson-Holland, aged 21, was a native of Victoria who was on leave from the Australian Navy. A handsome blond man, known affectionate as “Dutchy,” Dyson-Holland came from a military family and was an experienced diver and spear fisher. On this day he was accompanied by his friend Frederick John Baylis.

As the two made their way ashore, Baylis noticed a small octopus in the shallows, which he described as “red and green” with bright blue rings. Ignoring the creature’s flailing arms, Baylis scooped it up and played with the creature for several minutes, until he was distracted by a bright piece of coral. He tossed the octopus to Dyson-Holland, who was busy carrying the duo’s fishing ashore; the mollusk landed on his shoulder and crawled onto his back, where it settled for a minute before dropping off. Baylis, having evidently sated his coral curiosity, picked up the creature and threw it back into the ocean.

Soon afterwards, Dyson-Holland complained that he was having trouble breathing and that his mouth had dried. Dyson-Holland had a mild form of asthma, and Baylis worried that his friend was suffering an attack, but Dyson-Holland assured him that he was fine. A few minutes later, however, Dyson-Holland vomited violently and then collapsed on the beach. As Baylis ran into his friend’s aid, he noticed two small puncture wounds on Dyson-Holland’s back. The latter confirmed his suspicions, muttering “it was the little octopus” before losing consciousness.

After frantic attempts at resuscitation, Baylis drove Dyson-Holland to the nearest hospital. The doctors were vexed by his quick, complete collapse and placed him in an iron lung in a desperate attempt to save his life. Dyson-Holland died soon after being admitted, leaving behind a guilty friend, grieving family and a medical mystery that took years to resolve.

That octopuses are venomous was no secret to marine biologists, of course. Octopuses kill their prey (usually crabs and other mollusks) by biting them with their large beaks, then injecting poison. But no octopus possessed venom dangerous enough to harm humans; the average bite was no more dangerous than a bee sting. Although there had been rumored cases of serious envenomization, none of the known species of octopus had ever been classified as dangerous, outside lurid tales of giant creatures pulling men into the water.

Experts examining the case viewed as alarming and inexplicable, especially since the animal could not be studied based on Baylis’s description alone. Two doctors writing in the Medical Journal of Australia concluded that the symptoms were inconsistent with octopus envenomization, and that “the possibility of some hypersensitivity [allergic] reaction exists.” Other writers echoed their conclusions, including famous naturalist Roger Caras, who noted in his book Dangerous to Man (1964) that Dyson-Holland suffered from asthma which may have heightened reaction to an otherwise benign venom. Since the dangerous posed by the octopus “had not been adequately demonstrated,” Caras even speculated that “the youth had not been killed by an octopus at all.”

In the intervening years, however, several additional cases strengthened the case against the octopus. In 1961 two more young men were bitten by small octopuses, one narrowly avoiding death through emergency treatment. Then in 1967, twenty three year old James Arthur Ward (a young soldier with no history of respiratory ailment) was bitten by an octopus in the waters off Sydney, dying in hospital three hours later. This time, Ward’s mates captured the creature responsible: it was Hapalochlaena maculosa, the tiny southern blue-ringed octopus.

The blue ringed octopus, a group of four species native to the South Pacific, are small (rarely more than 8 inches) but highly venomous creatures. So named because their blue rings glow when excited, the creatures carry a deadly poison called tetrodotoxin, also found in puffer fish and certain species of newt. Tetrodotoxin causes complete paralysis of the body’s muscles, resulting in respiratory failure; it can only be treated by artificially respirating the victim until they pass the poison from their body. Scientists discovered that the octopus can carry enough poison to kill 20 grown men.

Fortunately, since the perpetrator was identified, no confirmed victims of the blue ringed octopus have died (though severe poisonings do occur). Today Australians know to keep a wide berth from this beautiful but deadly cephalopod. It’s also a good reminder that, no matter how tempting, it’s wise not to pick up, play with and certainly not toss around tiny animals – for your own sake, if not theirs.