Crocker was a henchman of Roland Daggett.
Crocker hired Nitro for his boss, and helped the explosives expert in his effort to blow up Crime Alley so Daggett could use its land to develop new real estate. Crocker also helped Nitro with setting up the explosives.
During the rigging, the two were interrupted by Leslie Thompkins. She recognized Crocker as an employee of Daggett, and when she saw the explosives Crocker and Nitro knew she had become a liability. They tied her up and left her behind, as they went to the old SRO Hotel, the last building that had to be rigged.
After they were finished, Batman visited them. He was already acquainted with Crocker, and was quite curious to know what they were doing there. He had already guessed Daggett's plan, and locked Crocker and Nitro in a truck full of explosives while he went looking for Dr. Thompkins.
Batman defused most of the bombs, and when the timer ran out, only a few condemned buildings were blown up. He confronted Daggett with the arson, but the slick businessman denied any involvement and Crocker and Nitro were arrested.