A career jewel thief masterminds a heist to steal a huge diamond but is apprehended by the police shortly after stashing the gem in an unfinished building. After serving two years in prison, he is released and immediately sets out to retrieve the hidden diamond, only to discover that the building he used as hiding place is now a highly secured police precinct. Determined to recover the gem, he decides to infiltrate the precinct by posing as a newly transferred detective. His quick wit, criminal expertise, and comedic flair help him navigate through the everyday challenges of police work, often leaving his colleagues bewildered by his unorthodox methods.

As he searches for the diamond, his charade becomes increasingly complicated. Accidental success in his faux-detective role earns him respect and accolades from the precinct, leading to deeper involvement in ongoing criminal investigations. Balancing between retrieving the diamond and maintaining his cover, he forms an unexpected friendship with a fellow cop who admires his seemingly uncanny investigative skills. Tensions rise as he gets closer to locating the hidden gem while managing to fend off suspicion and outsmart those who might uncover his true identity.