- "We have a signal now, for when I'm needed. But when that light hits the sky, it's not just a call. It's a warning."
The Bat Signal is a searchlight located on the roof of a condemned building. The signal is used as a method of contacting and summoning Batman in the event of a serious crisis or of assistance.
Having learnt that Major Don Mitchell, Jr. had been murdered, Jim Gordon went to the Bat Signal and sent out the call to Batman, seeking his help in the investigation. As the signal lit up in the sky, various criminals across Gotham City saw it, including a graffiti artist defacing the Gotham City Hall, and a criminal robbing a store. As they saw the signal, these criminals decided to return home, in order to avoid encountering Batman.
The signal was also seen by a member of the Train Gang, moments before they attempted to rob and murder an innocent bystander in the Gotham Subway, causing the member to become fearful of being ambushed. However, their efforts were stopped by the arrival of Batman, who proceeded to fight and defeat all of the gang members, saving the bystander, who remained terrified. Following this, Batman saw the Signal in the sky, and went to meet with Gordon.
Following his escape from the Gotham City Police Headquarters, Batman returned to the Bat Signal, where he met with Gordon to discuss the situation, with Batman reassuring Gordon that he did not believe he would be targeted by the Riddler, noting that Gordon was not corrupt, like the Riddler's other targets had been. As they stood by the Signal, Batman explained the links between the murders of Mitchell, Gil Colson and Pete Savage.
When Catwoman found out that William Kenzie was witnessed to Annika Kosolov's murder by Carmine Falcone, she found him, tied up and began to physically assault him on the roof of the GCPD. Catwoman also used the Bat Signal to contact Batman, who soon arrived there with Gordon, managing to prevent Catwoman from murdering Kenzie, and forcing Kenzie instead to confess to all of his and Falcone's crimes.