This article traces the history and reorganization of the Bureau of Investigation and Statistics (BIS) into the Secrets Bureau and examines the role played by the Secrets Bureau in the 228 Incident of 1947. In the early post-WWII years, the investigation team under the Taiwan Provincial Garrison Command had a dual identity of being the BIS-Taiwan Branch. Chen Dayuan (陳達元) served as the head of both the investigation team and the BIS-Taiwan Branch. In July 1946, the BIS-Taiwan Branch was reorganized into the Secrets Bureau and led by Lin Dingli (林頂立). Though separate and independent of each other, the investigation team and the Secrets Bureau worked closely together. The newly established Secrets Bureau comprised three divisions. By 1947, it further had five communication groups, a student movement group, and a worker movement group. To maintain its operations clandestine, pseudonyms were used in all contacts and exchanges between members, groups and organizations. Upon the outbreak of the 228 Incident, Chiang Kai-shek commanded Zheng Jiemin, the head of the Secrets Bureau, to send Liu Geqing (劉戈青) to Taiwan. Liu was entrusted with the tasks of assisting Chen Dayian to quell the unrest and to ensure the safety of Zhang Xueliang (張學良). During the 228 Incident, all branches of the Secrets Bureau were actively collecting information and intelligence. Some agents even infiltrated into the 228 Incident Management Commission to spy on the uprising and to influence its development. Through offering intelligence and advice to Chen Yi (陳儀), the BIS-Taiwan Branch gained Chen's trust nd attained greater authority to suppress the riots. Though being secret agents, they could work openly with the army and the police to arrest rebels and dissidents.