Lydia is Harriet Wheelwright's maid. Lydia gets some sort of cancer (John isn't too specific about it, but we're going to assume it's bone cancer) and has to have her right leg amputated. After that, Lydia can't really work anymore, but she continues to live at 80 Front Street with John's grandmother. We get the vibe that Harriet and Lydia are secretly besties in spite of Harriet's elitist attitudes. Harriet even gets Lydia her own maid! Lydia dies about a year after Tabby does.