Mrs. Slydes was the caretaker of The House on Haunted Hill, alongside her husband Jonas, for years. When Frederick Loren rented the house for a haunted house party, Jonas and Mrs. Slydes were to leave at midnight and lock the only door out; trapping the guests inside for the night until they unlocked the house at 8 AM.
Nora Manning sees Mrs. Slydes twice in the basement and mistakes her for a ghost. Later, shortly before midnight, Jonas and Mrs. Slydes come down to thee living room and Frederick explains the misunderstanding to Nora. When Frederick offers the guests a choice to leave at once with Jonas and Mrs. Slydes, or stay locked in the house for the night, before any of the guests can choose, Mrs. Slydes and Jonas leave a few minutes early, locking Frederick and the other guests in for the night.