Secret promises to be a gripping tale that explores the science of omens (Nimitha Shasthram), psychological turmoil, and the strength of friendships.

The story revolves around the clash between Ayyappan, a senior police officer who serves at the Attappadi Police Station and Havildar Koshi, who comes to the village with a motive.

The story is set against the backdrop of hills of Nilgiris where two siblings, Joshua and Jenny, who come from a middle-class family. Together, they dwell on the serenity and calmness of the mountains.