Daily Arc 004.
Summoned to Alaska to investigate some very strange goings-on, Don Winslow and Red Pennington will come up against one of the Scorpion's lieutenants who has been operating in that region, the Masked One. The would-be mastermind has been perfecting a "Radium Ray" shot from a "solaradium gun" which can kill unseen from a distance. With the larger model, he plans to use it to "defend our secret operations ... from all attacks by the U.S. Navy".