A British army officer refuses to avenge the death of a general who was murdered years earlier. He is awarded three feathers by his officers. When his fiancée fails to defend his stance, he plucks a feather from her fan. He proves his courage by rescuing his comrades in dangerous and life-threatening situations. Later he returns each feather as proof of his redemption and courage.

In 64 A.D., Marcus Superbus is Prefect of Rome. When the Emperor Nero decides to renew persecution of the Christians, Marcus opposes him, fearing for the safety of Mercia, the Christian woman whom he loves. Through the machinations of the Empress Poppaea and other women at court, Tigellinus, Nero's agent in the war against the Christians, convinces Nero to have Mercia arrested. Marcus appeals to the emperor for mercy, but is told that she can be saved only by renouncing Christianity. Waiting to enter the arena to be killed, Mercia steadfastly refuses to reject her religion, despite Marcus' pleas. Finally, Marcus is converted by her and they enter the arena to face death together.

The Span of Life is a 1914 drama film