Nancy is among the experiments freed when Fish Mooney escapes from the Indian Hill facility. Together with Sid, another experiment, Nancy captures Ethel Peabody and brings her before Fish in an abandoned warehouse. While Fish deals with Peabody, Nancy stands guard and ultimately catches young Ivy Pepper, who wanted to find out where her friend Selina Kyle was going. Nancy brings Ivy before Fish, who decides that she must die. Ivy wrenches free however and escapes, although she is pursued by some of FIsh's monsters, including Nancy.
Nancy, along with the rest of the group, is present at an old bank when the GCPD arrives to arrest them. She escapes with Fish and other monsters. Together with Sid, Nancy then kidnaps Harvey Bullock and brings him to Fish. From Bullock, they learn where Strange is being held, an old mansion outside of Gotham. They head there, but are forced to stay when the police arrives outside. As Fish still has Bullock, they can hold the police at bay, but not the angry mob turning up with Penguin who demands the death of Fish and her monsters. On guard again, Nancy catches Jim Gordon when he enters the mansion to free Bullock.
When Fish decides to escape, she leaves Nancy and Sid behind to cover their backs. Nancy and Sid wait in the entry hall of the mansion, shooting the hostile citizens with their guns. However, they are eventually overwhelmed by the angry mob and Nancy is thrown to the ground and bludgeoned to death by the mob and their crowbars. Her and Sid's corpse are later burned by the mob, who cheer because they managed to murder two of Fish's monsters.
- Nancy's attire is similar to that of Copperhead and Tabitha Galavan, two other Gotham villains.
- She and Sid were named after Sex Pistols bassist Sid Vicious and his girlfriend Nancy Spungen.