Nothing is known of the history of the criminal known as Mister Nitro prior to his entry into a hospital in New York City in June of 1945.  Carrying a spherical black bomb, he threatened to the destroy the hospital unless his demands were heard and met.  Fearing an explosion, the assembled doctors, including Charles McNider, listened as a man describing himself as Mister Nitro the Walking Bomb explained that he had injected himself with nitroglycerin for years, making a chronic risk for explosion. An abnormally large man, his potential for explosion was thought considerable and when he demand all the funds held at the hospital, he was accommodated and left with bags of cash.  As he left, he tossed the bomb was revealed to be a prop.  When the police arrived, they were cautioned not to engage Mister Nitro as an explosion of that much nitroglycerin would create a horrific blast.

From then on, Mister Nitro went on an impressive spree as his reputation spread across the city. He lifted gems from a jewelry store and emptied an armored car of cash in front of a bank.  He sat down at a restaurant and demanded the menu for free.  As he left, Dr. Mid-Nite began to approach but was restrained by the police fearing an explosion.  When Dr. Mid-Nite insisted that he be able to try, Mister Nitro pulls out a container of nitroglycerin and tossed them for explosive effect.  Defeated, the police and Dr, Mid-Nite retreated as Mr. Nitro declared that he would rob a nearby hospital to replenish his stocks.

After stopping off at a construction side to gather more ammo, Mister Nitro barged into the same hospital he had visited previously.  This time he demanded that doctors actually conduct an infusion, maximizing the amount of nitroglycerin in his system,  As the doctors were prepping him, Dr. Mid-Nite rushed in with what appeared to be a box of TNT and challenged Mister Nitro to a fight.  Horrified house staff watching and Mid-Nite directly engaged Nitro, ultimately causing him to fall out a window where a dump truck full of cotton previously arranged by him awaited.  With Nitro unable to get a footing, he was quickly wrapped up and carried back into the hospital.  There he was placed in a sweatbox where the constant caused the nitroglycerin in his body to evaporate, rending  him helpless and ready for jail (All-American Comics #66).

Whether Mister Nitro ever returned is unknown.