Adayalam (1991)

Latha (Rekha) who is running her father's business empire after he suffered a debilitating stroke, receives a call from a mysterious stranger Raji, threatening to reveal embarrassing details about her father unless she pays up Rs. 500,000. Since she has no idea how to deal with the blackmailer, she turns to Capt. Hariharan who runs a detective agency for help. Things take a grim turn when Raji, and then Latha's cousin Suresh, both turn up murdered one after the other. The evidence unearthed by Hariharan seems to implicate either Latha or her sister Malini - but are the girls up to murder to protect their dad's good name?