"The Fighting 69th" is a First World War regiment of mostly New York-Irish soldiers. Amongst a cocky crew, perhaps the cockiest is Jerry Plunkett, a scrappy fellow who looks out only for himself. The officers and non-coms of the regiment do their best to instill discipline in Plunkett, and the chaplain, Father Duffy, tries to make Plunkett see the greater good, all to no avail. Behind the lines or in the trenches, Plunkett acts selfishly and cowardly, eventually costing the lives of many of his fellow soldiers. A final act of cowardice leads to terrible consequences, but Plunkett sees in them a chance to redeem himself...if only he can.