54321: 5 people, 4 different lifestyles, 3 murders, 2 hours, and 1 ultimate revenge—everything unfolds within the walls of a single house. Vinoth, adopted into a loving family, grows up showered with affection, while their biological son, Vikram, is left feeling overshadowed and resentful. Years later, fate brings them together again, giving Vikram the perfect chance to settle his childhood grievances. But as vengeance takes control, the night spirals into a deadly game of betrayal, secrets, and murder.