Dr. Stone Season 1 Episode 4 Recap – Fire the Smoke Signal

Gunpowder

While they’re at the hot springs, Taiju finally opens up to Yuzuriha about what he wanted to say 3,700 years ago. But now that their circumstances have changed, he resolves to help bring back civilization first before he can get back to his confession. Yuzuriha nods, agreeing they should work together to build a better future.

Senku smirks as they find the three ingredients for gunpowder: their limitless supply of sulfur from the hot springs, a supply of charcoal from burning wood, and potassium nitrate, a substance that Senku prepared in advance using some of the fluid from the cave.

Mixing the three substances with sugar and pounding them together turns them into nuggets, but with Taiju’s great strength, their first batch explodes in their faces. Despite the accident, Senku remains proud of the finished product.

Yuzuriha asks if it’s enough to defeat Tsukasa, but Senku only plans to make a deal with him. Tsukasa isn’t a mindless brute, so they might leverage their negotiations with gunpowder. Still, they have to be cautious around him.

They adjust their formula to make a milder version of the gunpowder, but then Yuzuriha spots smoke in the distance. It couldn’t be Tsukasa because it’s in the opposite direction. Senku thinks it’s a smoke signal in response to the smoke their explosion caused. He thinks there are other humans besides them.

Smoke Signal

Senku gets a gut feeling that if they send another signal and find other people, their chance to succeed would be even better. They feed their gunpowder with more firewood to make the signal clearer.

Meanwhile, Tsukasa is gaining on to their location. He figures out that the fourth ingredient made from seashells is related to potassium nitrate. He sees the signal and learns that they’ve finally made gunpowder.

Tsukasa finds Yuzuriha and holds her hostage in front of Senku. Senku mocks Tsukasa, saying he won’t be the strongest if they manage to make weapons. Tsukasa doesn’t want that to happen arguing that it will cause death and destruction again.

Tsukasa asks for the miracle fluid formula. When Senku tries to talk him out of it, Tsukasa cuts through Yuzuriha’s hair and shocks them both. He figures out that Senku still feels affection for his friends and uses it as leverage. Yuzuriha thanks him instead for cutting her bothersome hair.

She offers to die as long as Senku secures the miracle fluid formula, but then Senku gives in and tells Tsukasa the formula. Miracle fluid is made of cave acid mixed with distilled alcohol, but only the perfect mix works.

Tsukasa thanks him. Yuzuriha cries.

Dreams of Science

While searching for firewood, Taiju finds three other smoke signals. There must be more people nearby.

Tsukasa lets Yuzuriha go and asks Senku to renounce all forms of science in exchange for his life.

Senku remembers his dreams as a kid of becoming an astronaut. He took up reading and doing experiments all on his own. His father even sold his car to give him all the tools and equipment he needed for his studies. Senju would make weird experiments and inventions while Taiju was there to defend and help him.

During middle school, they launched a rocket full of stuffed toys into the air using the culmination of Senku’s inventions.

Tsukasa asks him once more if he’ll abandon science. Senku doesn’t want to give it up, so he agrees to die. Tsukasa promises him a painless death, regretting that they could’ve been friends.

Our Thoughts

Senku and Tsukasa are really interesting. They’re not your clear-cut villains and good guys. It’s an interesting dynamic that makes predicting their actions very fun. 4/5.