One Piece — Episode 32: Witch of Cocoyashi Village! Arlong's Female Leader!

You are watching the episode Witch of Cocoyashi Village! Arlong's Female Leader! Zoro is captured by the fishmen after Usopp and Johnny ditch him, and it's revealed that Nami was part of Arlong's crew the entire time. When a group of Fishmen attack Cocoyashi Village, Usopp comes to the rescue.