Wu San

Wu San was a Chinese interrogator working for Cheng Zhi seven months after Day 5.

Before Day 6
During his time in China, Jack Bauer was tortured by men working for Cheng Zhi in order to uncover whether Hong Wai or Li was working with the Americans as an undercover agent in the Chinese government. Despite harsh treatment such as whippings and electric shocks, Jack did not speak a word. Wu San warned Cheng that the repeated torture would kill Jack, but Cheng persisted for a time. He then tried an alternative route: a ruse in which Jack believed he was extracted by two men claiming to be American rescuers. Jack then unintentionally betrayed Hong Wai.