She is portrayed by Maria Olsen.
She is a Fury sent by Hades to find Percy Jackson, who is suspected to have stolen Zeus's master bolt and Hades' Helm of Darkness. She manages to infiltrate his school by impersonating a maths teacher named Mrs. Dodds.
Some times later, Mrs. Dodds accompanies Percy's class during a school trip to a museum along with her colleague Mr. Brunner. During a lunch break, she witnesses Percy unintentionally make water from a nearby fountain grab the class bully Nancy Bobofit (who is Mrs. Dodds' favourite student), after she picked on his friend Grover Underwood. Mrs. Dodds then demands Percy to come with her into the museum. Percy follows her, but she turns back into her true appearance on the top of a scaffolding and attacks him. Luckily, Mr. Brunner, who is actually the centaur Chiron, enters the room and throws a pen to Percy, which turns into a sword. Percy uses the sword to stab Alecto, who vaporises.
However due to being a monster, Alecto doesn't stay dead for long and returns to her form as Mrs. Dodds alongside her two fellow Furies to pursue Percy, Grover and Annabeth Chase.