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 plans.
However, Tsai's true loyalty was to the Kuomintang and to its leader, Templar Grand Master 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 arrangements to have it stolen.
Later, the Black Cross Albert Bolden 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 speak about possibly killing Soong, and was swiftly knocked out. After he discovered Chiang Kai-shek's treachery, the Black Cross sent Tsai to tell the general that the former was coming for him.