In the first 'Scream', Tatum Riley is the best friend of the protagonist, Sidney Prescott. She and her friends live in Woodsboro, California and attend the local school, Woodsboro High. Her older brother, Dwight "Dewey" Riley, is the Deputy Sheriff of the town, and her boyfriend Stu is part of her school clique.
We first meet her when she appears suddenly by Sidney's side at school to talk about the two murders that took place the night before. She may be interpreted as a gossip thanks to this introduction; however, with the media around and other students buzzing with the news, it seems to be a very popular subject in general.
Tatum may also come across as quite outspoken and independent. Whereas some women do not speak out against offensive remarks made by their partner, Tatum reprimands Stu when he makes what she believes to be a sexist comment. Her direct approach may result in her appearing insensitive at times, such as when she suggests Sidney's murdered mother did have affairs (as the town rumours suggest). However, she is obviously a caring and protective friend; inviting Sidney to sleep at her house after the first attempt on Sid's life, and later - amongst other incidents - comforting her regarding the attacks and Sidney's mother's death.
Despite promising to pick Sidney up at 7PM/19:00 in one scene, she is quite late, which perhaps suggests an un-reliable or tardy quality.
In spite of being the younger sibling, she appears to be bossier and more assertive than her brother, who she does not seem to have much respect for. She humiliates him in his work place, again showing a more insensitive side.
During a party at Stu's house, Tatum sadly loses her life after going alone to the basement, where she is trapped by the killer. Here she demonstrates a courageous side to her personality when she attempts to wound and escape the perpetrator. However, upon attempting to exit through a cat-flap on the garage door, her neck is snapped and she is electrocuted when her attacker flicks the switch to lift the door. She is last seen when a distraught Sidney finds her corpse hanging from the door.
Before she dies, Tatum refers to the masked man as "Mr. Ghost Face". "Ghost Face" has since become how this particular costume is known.