Other notable cast members include Lissy, S. S. Chandran, Nassar, Somayajulu, Kovai Sarala, Baby Sangita, and V. M. C. Haneefa.

During every New Moon, a spirit possesses an elderly woman and ruthlessly murders anyone staying in a particular room.

Somaiya reveals that the ghost is the spirit of a young girl who died due to a fire accident caused by students during Diwali–the Hindu festival of lights–who stayed in that cursed room.

Raghuvaran performs a powerful Pooja based on his occult studies and rushes to save Rajasekar and Radhika, who have volunteered to stay in the haunted room to kill the ghost.

The ghost, now possessing her bedridden grandmother, transforms into a strong entity armed with a large sword, she attempts to kill Rajasekar and Radhika, but Raghuvaran intervenes just in time.

After a prolonged struggle, Raghuvaran manages to stab the grandmother with his Trishula, causing the ghost to leave her body and enter a nearby python.

Raghuvaran eventually succumbs to the flames, fulfilling his promise to sacrifice himself and end the ghost's reign of terror.

[3] N. Krishnaswamy of The Indian Express wrote, "From family melodrama to murder thriller, to a horror line about spirits of dead persons hungering for revenge, Pagalil Pournami traverses a range of story scenarios haphazardly."