A disaster at Chalmers Laboratories involving radium kills Brett Bryson. His bosses are tried for negligence but acquitted. A hooded figure later robs a jewelry store, leaving a watchman dead of radium burns. Superman is implicated, and he must clear his name before Sgt. Casey arrests him.; Zatara performs in Patona, a far-off kingdom, winning the Queen's confidence. She asks him to help her get the Zin Diamond to the Capital Bank of America. Bem, an international jewel thief, plans to get rid of Zatara and steal the diamond.; While on patrol, Mr. America spots some thugs kidnapping a man and stops them, although he is distracted by an explosion at the Mains Aircraft Factory. He manages to tear a piece of a thug's jacket away that bears an insignia. The man was Ed Blake, photographer, planted by the Globe newspaper at a spy camp but discovered. Mr. America decides to use the insignia to infiltrate the spy camp. There he meets Doris Dare, a reporter, who tells him that they must stop a package from being mailed.; When Midwest College's baseball team loses their pitcher, Jerry Hope, to a strain, Pep must stand in to pitch the game without any relief. Seeing an opportunity, "Odds" Renaldi and Monk, gamblers, make a plan to fix the game.; Flying overhead, the Aces see the serum sled bound for Glencarren to help with an epidemic. As they pass, the sled-driver, Angus, is shot. In Glencarren, at Douglas MacLean's the Three Aces learn of the death and decide to intervene.; In Cairo, Congo Bill consults with a British officer about a hidden submarine base from which u-boats are operating. The officer needs Congo Bill to help locate the base along the north African coast.; Jon Valor, posing as Noah Scott, trader, has been invited to attend the royal ball as a guest of his friend, Captain Don De Avila. Unknown to the Black Pirate, De Avila has laid a trap to capture him once inside the palace walls, and so regain the favor of the King of Spain.