Gladys Hickson was one of the support staff working in the Front Half of The Institute in Maine.
Gladys attended college for three semesters, and had originally planned on becoming a chemistry major. After she brutally attacked another female student, convinced that she was a rival for Gladys' boyfriend's affections, the college asked her to leave. She complied and quit, and soon after joined the U.S. Marine Corps. Sometime after her service, Gladys was hired to work at The Institute.
During the events of the novel, Gladys was well-known as one of many fake-friendly staff at The Institute. She would bring the kids here and there as required by the daily schedule. After Luke's escape, as things unraveled swiftly, Gladys grew more and more openly eager to murder the remaining children. She volunteered to set up a chemical mixture that would dump poison gas into the Back Half's HVAC system, and did so when Luke Ellis returned in an effort to save the other children.
Gladys' plan succeeded; the trapped children were all killed by the gas save for a tiny few who got out in the last moments. As the Front Half of the facility was ripped out of the ground and destroyed, Gladys struggled to maintain her balance as she tried to run across the roof. Her boss, Trevor Stackhouse, watched as she was thrown off the buckling roof and into the darkness. Stackhouse heard Gladys scream before she disappeared.
Gladys maintained a cheery disposition at work, but only at first glance. She would prop the look up briefly if the children provoked her in any way (which never took much), and after that would quickly turn nasty. Trevor Stackhouse observed her to have a fiery and savage temper; the beating of her college "rival" was not her first such outburst. The Marines briefly suited her, but The Institute was much better; Gladys was allowed and even encouraged to hurt people there. She was not only able to live with what she was doing, but was quite glad to be a part of it. The true extent of her cruelty, however, was not revealed until the final hours of her life, when she stood by her boss, Trevor Stackhouse, even as the rest of the staff deserted in growing numbers. Trevor Stackhouse found Gladys' attitude unsettling but encouraged her behavior regardless.
The former Marine was feared and hated universally by the children at The Institute. No one among the survivors appears to have mourned Gladys' demise.