Twin sons are born to King Louis XIII of France. Despite the best efforts of the legendary adventurers the Three Musketeers, the power-hungry Cardinal Richelieu kidnaps one of the princes to be raised in secret and one day ignite a revolution. The other child is placed under the care of the Musketeers' old ally D'Artagnan, who raises him to take his father's place as king. Shortly after his coronation, the new king is captured by Richelieu's followers and replaced with his long-lost sibling. With the future of France hanging in the balance, D'Artagnan must bring together his old friends Athos, Porthos and Aramis one last time to free his former charge from a lifetime of imprisonment behind an iron mask.

The Iron Mask is the final silent feature for famed screen star Douglas Fairbanks. Worried that his voice would not be strong enough for the arrival of sound, Fairbanks saw The Iron Mask as his last hurrah and spared no expense on the film's lavish production. He had previously played D'Artagnan in A Modern Musketeer (1917) and The Three Musketeers (1921). English actor Nigel De Brulier's performance as Cardinal Richelieu proved so popular with audiences that he would return as the character in the later The Three Musketeers (1935) and the remake The Man in the Iron Mask (1939). William Bakewell, who plays the dual role of the two princes, would have a long career in Hollywood, appearing in films ranging from Oscar winners like All Quiet on the Western Front (1930) and Gone With the Wind (1939) to B-movie fare such as Radar Men from the Moon (1952).