Formerly a corporal in the U.S. Army, Leonard "Len" Brown was an employee of T.H.U.N.D.E.R. who was stuck in a desk job and not happy about it. But T.H.U.N.D.E.R.'s inner council called upon him to wield an invention of the late Professor Jennings, an “electron molecular intensifier belt” or “Thunderbelt” (as he called it). Len Brown became the T.H.U.N.D.E.R. Agent Dynamo. Besides Iron Maiden, other foes of Dynamo include Red Star, Doctor Sparta and a mysterious race of alien invaders.