Rock Hudson stars as Michael Martin, a naive and impetuous young would-be rebel in 1815 Ireland, who turns to robbery in his desire to support the cause against England. Now wanted by the British and forced into hiding, he crosses paths with the renowned rebel leader Captain Thunderbolt aka John Doherty (Jeff Morrow), who takes him under his wing. Impressed with Michael's bravery, Thunderbolt makes him his second-in-command, a job that becomes twice as difficult when Thunderbolt is wounded and must drop out of sight. Michael must replace him, not only as a rebel leader, but also in running the business that Doherty fronts as a cover, and in his household -- and that puts Michaal on a collision course with Doherty's equally impetuous, headstrong daughter Aga (Barbara Rush). Sparks fly between them, as the English draw ever closer in their pursuit of the rebels.