Thimmarusu is the remake of Kannada movie Birbal (2019). On a rainy night in 2011 when a cab driver, who is also a police informer, is brutally murdered. Vasu who is passing by and informs the police, is framed and sentenced. Eight years later, Ramachandra re-opens this case when the cash-rich legal firm he works for decides to take up a few cases free of cost for those who cannot afford legal services.
Helping Ramachandra crack the investigation are Anu and Sudhakar. In a partly Rashomon effect attempt, Ramachandra tries to look at the crime from different points of views. A few twists throw the investigating legal trio and Vasu off balance, until Ramachandra reveals all his cards and gets to the bottom of the puzzle.