In November, 1971, India and Pakistan are on the verge of declaring war on each other, as a result of the refugee crisis precipitated by the Pakistan Army under Operation Searchlight. The Indian Navy and RAW decipher a secret code sent from Pakistan to East Pakistan (modern-day Bangladesh), relating to a possible attack on an Indian naval vessel. The Navy deduces that the target may be "INS Vikrant", India's sole aircraft carrier. The top command dispatches the submarine "S21", under the command of Cmdr. Ranvijay Singh for recce missions. To temper Singh's belligerent tendencies, the Indian Navy Admiral assigns Lt. Cmdr Arjun Varma to "S21", with orders to ensure that Singh does not confront any Pakistani warships and trigger a war.