An assassin named Street Moon is assigned to hunt down a Runner; a person who is meant to deliver and receive illegal material and fight against the government, or Watchers. Runners want to get rid of society's Tell, an implanted organ in citizens that allows the Watchers to monitor them. Street Moon and many other bounty hunters are constantly on the lookout for Runners in order to collect rewards. Street Moon tracks her target down but has trouble focusing. For some reason, she keeps having flashbacks of her former lover, Sly, who left her for her best friend. She begins to remember the pleasant memories they had together, but mostly remembers the emotional pain he caused. This messes up her hunting skills, and causes her to experience uncontrollable daydreaming and headaches, yet she can't figure out how to stop it, even while she works. She loses the Runner's trail and goes to one of her usual bars for a drink when a group of Watchers bursts in, on the hunt for him. The bartender, MoDupe, is accused of obtaining and selling Purge, an illegal substance which is ingested for the sole purpose of getting rid of the Tell. Its use is punishable by death. MoDupe has to go on the run, but brings Moon with him as he has been secretly giving her Purge. MoDupe wants to have her freed so that she can become a Runner and help people in the city.