The film's screenplay by Douglas Fairbanks Jr. is based on the novel of the same name by Justin Huntly McCarthy.

Nearing the end of the 18th century, Napoleon's vast army is sailing towards the Irish coast.

The national poet and freedom fighter who goes by the name of "The O'Flynn" is traveling back to the castle where he was born, when he encounters a coach being robbed by rogues.

Lady Benedetta eventually agrees to take up the invitation from the elegant O'Flynn, who rode ahead to prepare the castle.

O'Flynn is attracted to Lady Benedetta, and when he finds out that her fiancé, Lord Sedgemouth, is in favor of Napoleon, he challenges his rival to a duel.

He is brought in front of Napoleon's general, Van Dronk, and they spend the night drinking together.

When the general passes out, O'Flynn puts on his uniform and tries to steal the new plans for invading Britain.

He manages to make the French ships near the coast to turn back by signaling to them from ashore.

The movie was based on a play The O'Flynn by Justin Huntly McCarthy which premiered in 1910 starring Sir Herbert Tree.

It was set in Ireland during the reign of William of Orange and dealt with the attempt of James II to retake his throne.