Mrs. Gates is the housekeeper at the Red House. She is snobbish and class-conscious, but this behavior allows the police to work out when the body was put into the grave - Mrs. Gates noticed when her simple and "appropriate" wreath for Lady Thorpe's grave was moved aside, contrary to her very strict instructions.
Her snobbishness give the reader a disagreeable impression of her, but she can also be seen as a comic character; Inspector Blundell certainly can see the comic side of her snobbery. However, Mrs. Venables disapproves of her behavior, stating that her snobbery leads her to neglect some of her duties as the head of the Red House servants.