Lucy Armstrong is a student at the Wayward Pines Academy and the sister of Frank Armstrong.
Lucy's parents died on Invasion Day, so she and her brother live at the Academy with the other orphans. She was assigned to assist Rebecca Yedlin in her beauty salon. When Lucy gets her period for the first time, she feels unready to become a mother. She fears that Megan Fisher will find out she is viable to reproduce and force her to be paired with another member of the First Generation so that she can start having children. Lucy confides in Rebecca, who takes Lucy under her wing and defends her against Megan.
She is then separated from her brother, Frank and is placed into Group One (the group that gets to go back to sleep into the Mountain).