Tsai was a Chinese barman working where the Master Templars of the Shanghai Rite were regularly meeting. Tsai was trusted enough to be the only one staying in the bar while the Templars were discussing about their Order plans.
However, Tsai true loyalty was to the Kuomintang and to its leader, the Master Templar Sun Yat-sen, and after Sun was killed by Assassins to his wife, Soong Ching-ling. While a Templar herself, Soong was not invited to the meetings as she was not a Master so she used the devoted Tsai to stay informed on Templar business.
In 1927, Tsai learned that the Templars were about to deliver a mysterious box to Chiang Kai-shek, the new leader of the Kuomintang, as a prelude to his induction into the Templar Order. Not trusting Chiang, Soong decided to prevent the general from receiving the package and made arrangement to have it stolen.
Later, the Black Cross who was investigating the theft, correctly guessed that Tsai was the key to uncover the culprits and forced him to reveal him everything. Tsai eventually led the Black Cross to his mistress, but made the mistake of jumping on him when he heard him spoke about maybe killing Soong, and was swiftly knocked out. After he discovered Chiang Kai-shek's treachery, the Black Cross sent Tsai to deliver a message to the general, a black cross to let Chiang know that he was coming after him.