The Fighting O'Flynn (1949)

O'Flynn, a soldier of fortune, returns to Ireland during the Napoleonic wars just in time to save Lady Benedetta from robbers, but they pursue her to ruinous Castle O'Flynn, after secret papers she carries which would reveal Napoleon's plans to invade Ireland. The Napoleonic agents (and British traitors) will stop at nothing to gain their ends, but the swashbuckling exploits of the O'Flynn may be a match for them all.