GR-74, commonly known as "The Ghostrunner" or "Jack" is the protagonist of the Ghostrunner series. He is the 74th Ghostrunner, and is presumed to be the last one active. The name Jack was given to him by The Climbers, as Zoe claimed when they found him and tried to repair him that he was all "jacked up", or that they had hit the "jackpot" in finding him.