Netitia (Nettie) Cobb is the housekeeper and friend to main character Polly Chalmers in Needful Things. After a lifetime of physical abuse first from her mother, then her husband, Nettie suffers a psychotic break and murders her husband. When Needful Things begins, she is a parolee from Juniper Hill Asylum, living alone but for her faithful dog, Raider (a gift from Polly the Spring prior). An initial reference is made to a deep-seeded hatred between Nettie and Wilma Jercyck over the dog.
The devil's bargain Nettie makes with Leeland Gaunt begins with an exchange of carnival glass for a promise. The promise is later called in with demand that Nettie paper the inside of Buster Keeton's house with pink traffic violation slips marked up with taunts.
As the climax of the story approaches, Nettie's dog is murdered by Hugh Priest, and Wilma gets the blame. This leads to a final confrontation between the two women, with Wilma killing Nettie with a kitchen knife, and Nettie killing Wilma with a meat cleaver.