Jack is infected with a bit of Aku and the piece infects him with Aku, trying to take him over and drive him to evil.

Samurai Jack Season 4 Episodes...

• s04e01 - XL: Samurai versus Ninja
• s04e02 - XLI: Robo-Samurai versus Mondo Bot
• s04e03 - XLII: Samurai versus Samurai
• s04e04 - XLIII: The Aku Infection
• s04e05 - XLIV: The Princess and the Bounty Hunters
• s04e06 - XLV: Scotsman Saves Jack (1)
• s04e07 - XLVI: Scotsman Saves Jack (2)
• s04e08 - XLVII: Jack and the Flying Prince and Princess
• s04e09 - XLVIII: Jack versus Aku
• s04e10 - XLIX: The 4 Seasons of Death
• s04e11 - L: Tale of X9
• s04e12 - LI: Young Jack in Africa
• s04e13 - LII: Jack and the Baby

Samurai Jack Show Summary

Made by Genndy Tartakovsky, this cartoon tells the story of a great warrior displaced to the distant future by the evil shape-shifting wizard Aku. The world has become a bleak place under the rule of Aku, segregated into fantastic tribes and ruled by Aku's evil robot warlords. Jack travels this foreign landscape in search of a time portal that can return him to his home time so he can 'undo the future that is Aku!'.