Keen Detective Funnies #21

This anthology issue features multiple detective stories, with "The Masked Marvel" as the headlining story involving a masked hero leaping from a ship to combat the "Mad Raider" and his pirates at sea. Another story follows soldiers in a World War I trench setting, where they detect enemy snipers positioned behind outposts and must warn their comrades of the danger. A third story depicts "Tick" the detective shooting at a crook, resulting in the crook's arrest, though Tick must then convince two criminals to testify against the suspects rather than flee. The final featured story involves "Spark," a radio operator who infiltrates a criminal gang's headquarters, coordinates with police and military forces to stop a planned raid on arsenals and battleships, and ultimately prevents the criminals from escaping.