Johnny, who witnessed Nami's actions from a distance, reports to the rest of the crew that Nami has murdered Usopp.
This episode is highly regarded for its "shock value," setting up the emotional backstory for Nami that is fully revealed in the subsequent episodes. One Piece Episode 33
Earlier in the episode, Zoro escapes his confinement after Arlong discovers the damage he caused to the base while Nami was secretly assisting him. Watch Guide & Trivia Johnny, who witnessed Nami's actions from a distance,