Mrs. Medlock holds the position of head housekeeper at Misselthwaite Manor. She rigorously upholds the household rules set by Archibald Craven, ensuring strict order during his absences. Her responsibilities involve supervising the staff and managing the manor's daily operations.

She initially restricts Mary Lennox to specific areas of the estate, forbidding access to forbidden sections. Mrs. Medlock actively thwarts Mary's attempts to investigate mysterious nighttime cries, intercepting her searches for their source. Together with other staff, she participates in hiding Colin Craven's existence from Mary.

Her authority includes disciplining perceived misconduct, such as confronting Mary about unauthorized wandering. After Colin is discovered, she continues to control access to him according to established protocols. Mrs. Medlock's strict enforcement lessens as the secret garden is restored and family relationships mend, though she maintains her formal role overseeing manor operations.

Her background before arriving at Misselthwaite Manor remains undisclosed. No significant personal development or changes to her responsibilities occur beyond this initial portrayal.