Racing against time, Shekhar and Jayavrat hunt for clues across Calcutta left by the scientist Gupta, aiming to find a vial with the secret gas formula. As they near the final code, Shekhar faces M in a deadly struggle.

Mrs. H & Pintoo are held hostage at Khasha Blanca forcing Shekhar to confront his past where he had uncovered a deadly gas weapon linked to M, a criminal mastermind. Now they must find the vial or his friends lose their lives.

Iraboty's arrival in Lonpur sparks intrigue as she convinces Shekhar to investigate the 150-year-old Skhondokhata legend in Purulia, linked to recent deaths in the Bhaskar family. Shekhar suspects a deeper conspiracy.

Shekhar & ex-army doctor Jayavrat Saini team up to solve a series of murders in Lonpur marked by a "horse shoe" symbol. As Jayavrat evolves from roommate to partner, a shadowy figure known as "M" ominously watches Shekhar from the shadows.

Shekhar & Jayavrat are in Bihar for a blackmail scandal involving a famous politician. Shekhar is fascinated by the enigmatic Iraboty, while Mrinmoy discovers a classified file on "M," adding a new layer of intrigue to their investigation.

Shekhar dives into a village scam where a jungle adventure leads to a bank heist. With a bride-to-be's father missing, he uncovers a tangled plot revealing a cunning robber with a grudge, while the looming threat of "M" draws ever closer.