A handful of Southerners united in the Irish Gang carry out numerous robberies in Mexico, crossing the border into Texas! On their trail are the rurals, a man from the arms dealer Gutierrez, Shane O'Donnell (former leader of a group of Fenian extremists, the Invincibles) and the pards. Tex had met some of the criminals shortly after the Civil War, when they were mercenaries of Emperor Maximilian against President Juarez. Also joining the hunt are Danny Moran, an old fighting buddy of O'Donnell, and Pat Mac Ryan, tracked down in Galveston during a boxing match! Shane O'Donnell, a Fenian revolutionary chased from Ireland by his own leaders, helps the Irish Gang break out two accomplices from a Mexican prison. The plan is to grab the fabulous treasure of Emperor Maximilian, currently protected by an army of outlaws armed to the teeth and led by General Carrasco and Habsburg Colonel Herzfeld! The pards must bring the Irish back to the United States, where they will be pardoned for the crimes committed in Texas, but they want to make the last coup and, with Pat Mac Ryan hostage, they force Tex to support them. The bloodthirsty general Carrasco would like to hire the Irish Band, but the Fenian revolutionaries rebel and the pards raid the Mexican fort, causing pandemonium to break out, made worse by a deadly machine gun operated in turn by Carson and Tex. When Montales arrives with reinforcements, he finds only rubble, and the Emperor's treasury is returned to the rightful government! But it's not over: the arms dealer Gutierrez, for whom Shane was supposed to find the gold, pays Moran to betray and kill his friend. The pards avenge him, but O'Donnell dies, dreaming of Ireland.
