WARNING: The following article contains spoilers for Season 1, Episode 12 of Dr. Stone, "Buddies Back to Back."
So far, little has challenged Senku as much as Tsukasa -- the all-mighty brawn opposing the former's considerable brain power. However, though Tsukasa has proven to be a life-threatening adversary for the planet's foremost scientific mind, he's dethroned in Dr. Stone's latest episode as the Stone World's deadliest presence... by poison gas.
In their ongoing quest to create a cure-all drug for Ruri, Senku's Kingdom of Science is in need of sulfuric acid. Knowing how treacherous collecting the substance will be, Senku silvers Ginro's spear and instructs him to head up an exploratory group of himself, Chrome and Kohaku as they head to an "emerald green" pool that's rich with the acid. "Silver reacts with hydrogen and turns black instantly," Senku explains, just as, to illustrate his point, the tip of the bodyguard's weapon starts to look charred as they approach the water.
The intoxicating combination of hydrogen sulfide and sulfur dioxide in the air is visualized in the episode as a mirage-like image of a beautiful woman who calls to Ginro like a siren. Bewitched, he approaches, not noticing his blackening spearhead. When Kohaku pulls him back, the dream turns into a nightmare -- much like The Shining's ghostly Old Woman -- and Ginro sees from the dying crows falling from the sky into the acidic water what would have happened to him. The gas is so poisonous, it kills living things instantly.
Heading back to their camp, the group is thoroughly discouraged by the problem at hand. Kohaku is willing to risk everything for her dying sister, while Ginro vows to never return to the terrifying lake of death again. As usual, Senku uses the benefit of his encyclopedic memory to find the perfect solution: gas masks. Powered largely by de-toxifying charcoal, the masks he whips up will still need testing, however.
At first Senku tries to order Chrome to stay behind while he undertakes the risky mission alone, not wanting to place all of his scientific eggs in one basket should the masks fail to protect them against the gas. Chrome is having none of it, however, even accusing Senku of being a "patronizing asshole." Amused, Senku agrees to let his protege accompany him after all.
Things go well for a short while as, back at the pool, the masks do their job. But one small slip on the rocky shore soon has Senku regretting giving in to Chrome's demands: Chrome starts to fall towards the water with his partner nowhere near enough to catch him. Thankfully, Ginro -- wearing an extra mask crafted by Kaseki -- overcomes his fear to show up just in the nick of time, extending his spear out for Chrome to steady himself with. With the vital material collected at no loss of life, Senku proudly announces that they've "overcome the biggest hurdle" yet.
New episodes of Dr. Stone air every Saturday night as part of Adult Swim's Toonami block, and are available on Crunchyroll.