The Iron Mask (1929)

King Louis XIII of France is overjoyed when his son is born, an heir to the throne. However, the Queen has actually given birth to twin boys, and Cardinal Richelieu sees the second son as a potential threat to the peace of France, so he has the boy sent to Spain to be raised in secret. This leads to Constance, D'Artagnan's lover, being sent to a convent. D'Artagnan rallies the Musketeers to rescue her, but Richelieu outsmarts them and banishes the group. Richelieu then enlists D'Artagnan to protect the young prince. Later, de Rochefort learns of the twins and Richelieu's plan, and kidnaps the second twin, raising him in secret. Years later, with Richelieu dead and the young prince crowned as King Louis XIV, Rochefort launches his plan and has the king kidnapped and replaced with the twin, who is masked and held prisoner in a remote castle. D'Artagnan is alerted by Louis XIV and realizes that only the Musketeers can help, so he reunites the group to stop Rochefort's evil plan, but at a great cost.