FBI agent, Harry Gannan was partnered with Jack Stone. On April 7, 1997, they were assigned to investigate possible sabotage in New York at the U.S. Online Company. While a Gremlin was the culprit, Stone began to suspect the Extreme Ghostbusters. He quickly had background information compiled on each of the four. After following them back to the phone company, Stone and Gannan were accidentally fired upon by Garrett Miller.
Stone had them arrested on charges of terrorism, sabotage, breaking and entering, and assaulting agents. However, while the team were being transported to Washington D.C., the agents inspected the Ghost Trap and released the Gremlin. Gannan was more sympathetic of the team and allowed Garrett to use his cell phone to make a call to Egon Spengler. Egon arrived just as the federal transport left the airfield so he sent Slimer to stow away on the plane. They were convinced of the Extreme Ghostbusters' innocence upon meeting Slimer. Stone didn't think anyone would believe it and created a cover story about microwaves from a surveillance satellite as the culprit. Meanwhile, details of the case were sealed in a classified file labeled "G1027."
Harry Gannan appears to be a rookie agent and displays naivete when dealing with the team. He lends Garrett his phone thinking they were entitled to one phone call, such is the case when arrested by the police. Gannan is also more down to earth than Stone. When learning a Gremlin is the real enemy, he immediately thinks of the Twilight Zone episode like Eduardo Rivera did prior in the day.
- Garrett's encounter with Stone and Gannan leads him to be distrustful of the FBI and this is brought up in "Eyes of a Dragon"