Queen Kunti abandons her first-born (born before her marriage from Sun God by using her special powers) in the river, who is then adopted by a charioteer Adhirathan and named Karnan by a sage. He was born with earrings and a protective armour. Karnan (Sivaji Ganesan) grows up to be a great warrior. Years pass and Karnan becomes a skilled archer. When he is insulted at a public archery competition for belonging to a lowly class, Duryodhana (S.A. Asokan) appoints him king of Anga Desa (one of his territories) and embraces him as a friend. Karnan is eternally grateful for this and chooses to fight on Duryodhana's side against the Pandavas, even when Kunti reveals that she is his mother and the Pandavas are his own brothers. Karnan is known for his generosity and never says 'No' when anyone asks him for something. Lord Krishna (N.T. Rama Rao), who supports the Pandavas during the Kurukshetra war, appears in disguise and asks for Karnan's protective armour and earrings, which he nobly gives away. Karnan is killed by Arjuna (Muthuraman) in battle, but becomes immortal with the blessings of Lord Krishna, because of his magnanimity of donating all even at the last minute of his life.
[from the book Pride of Tamil Cinema: 1931 to 2013 by G Dhananjayan, Blue Ocean Publishers, 2014]