Mr. Five By Five
An unknown arsonist is burning down buildings and the only clue is fiddle playing is heard before each fire. Superhero The Puppeteer (really Alan Hale) gets involved immediately when a benefit show he's starring in is set on fire. He discovers that delicate glass globes of flammable liquid are set in the building, then broken through sympathetic vibration via violin, setting the fire. Turns out it's the oddly named Mr. Five By Five, a violinist with a "Nero complex" who got the bum's rush from the benefit show.
Later, he drops incendiary leaflets on the town from a plane. When the Puppeteer tries to stop him, the plane crashes in the water, and that's seemingly the end of Mr. Five.
He takes his name from a goofy 1942 hit song, "Mr. Five by Five" written by Don Raye and Gene DePaul.