Nitro was an arsonist and explosives expert for hire.
Roland Daggett wanted to redevelop the old Park Row district, but found opposition in the residents and the city's zoning board. So, he tried a different approach. He hired Nitro to blow the block up. Nitro agreed, and set up a plan in which it would appear a gas main ruptured.
Daggett liked the plan, and ordered him to rig the block so it exploded at nine o'clock, when Daggett was conducting a speech nearby. With Crocker, Nitro placed the explosives, but they were interrupted by Leslie Thompkins. She recognized Crocker, and connected the two and the explosives to Daggett. With the danger of being exposed, Nitro and Crocker overpowered her. Crocker tied her up while Nitro finished the explosives. They then went to the old SRO Hotel, leaving Dr. Thompkins behind. After they finished at the hotel, Batman showed up. He saw them through almost immediately, and locked them both in a truck full of explosives.
Batman defused most of the bombs, and when the timer ran out, only a few condemned buildings were blown up. Batman confronted Daggett with the arson, but the slick businessman denied any involvement and Nitro and Crocker took the fall.
Nitro may have been based on "Nitro" Nelson, a Golden age Batman villain who was, like this Nitro, an explosives expert, and is very similar in appearance. Nelson's first and only appearance was Batman #58, where it is established that he had earlier, off-screen crimes and was sent to prison by Batman.