One Piece Episode 591 English Subbed Episode Title:Chopper's Fury! The Master's Inhumane Experiment!.Episode Description:The children and the Straw Hats were in a cave with Brownbeard tied up talking about the Master. Zoro, Sanji and Brook go to look for Kin'emon, who had gone to look for his torso. The children then started to fall over in pain while asking for candy. Chopper, who had been testing them for any sickness, revealed that they had been given a highly addictive drug and were suffering from withdrawal. They attacked the Straw Hats, who couldn't fight back without injuring the children, and eventually Usopp used his Burst Sleep Star attack put them to sleep. Back in the lab, Law gave Smoker's heart to Caesar, who had sent the Yeti Cool Brothers to deal with the Straw Hats. The Yetti Cool Brothers were then shown talking to each other while Zoro, Sanji and Brook were lying unconscious nearby.