第 4 集: Senku 打造蒸汽火車，Chrome 則被 Tsukasa 俘虜並審問。
Nikki and Senku discuss bringing more men from Tsukasa's Empire to their side. Chrome surrenders and is captured by Ukyo. Magma returns to Ishigami Village. In the village, Kaseki finished building a wheel. Senku creates blueprints for a steam engine vehicle. Using beeswax, Senku creates a mold for pistons and other parts. At Tsukasa's headquarters, Chrome declares to teach Tsukasa how amazing science is. Hyoga dangles Chrome at the waterfall while Tsukasa interrogates him. Tsukasa wants Chrome to betray Senku and the village in exchange for Senku's head and the village's safety. When Tsukasa asks Ukyo what Chrome was doing, Ukyo lies saying he found him possibly scouting caves. Back at the village, Senku finishes making the locomotive. (Source: Wikipedia)