It’s 2005. A van full of people traveling from Navamalai to a city nearby is forced to take a detour through the village of Kattiyal. The van goes missing in the forests, leaving Sakthivel and Karunagam bereft with grief at the loss of their children. In the present day, Gautham and his family set off on a road trip one fateful night when a detour down the same route changes their lives forever.

The mercenaries led by Farhan make their way through the forests as Farhan realizes that Jagan is holding back Prakash’s actual plans. Karunagam reveals the secrets behind Kattiyal and its devastated state, Shakthi's bigoted father, Sairaj, and his descent into madness. The four men venture deeper into Kattiyal only to be attacked by mutant-like creatures that lead them to fall into a cavern.

As Gautham and the gang realize they are in the old mining caverns of Kattiyal, they head deeper in and stumble into Sairaj’s new lair. The mercenaries enter the abandoned factory and find their way down to the underground lab, where they encounter a grotesque prayer altar made by the mutants.

Meanwhile, Gautham and his group barely escape the gruesome mutant giant Vettaiyan and stumble upon a horrific tribute in the caverns for the Mother-Goddess that causes Shakthivel to spiral. The group then manages to find Gautham’s family only to be on the run from the mutants.

With many lives lost, the mercenaries and Gautham’s gang finally get together and hatch an escape plan. But, the obstacle that stands in their way is the giant mutant monster, Vettaiyan, and his army.