Aunt Agnes, or "Aunt Agony," as the twins lovingly call her, is Sophie and Josh's 84-year-old aunt with whom they are spending the summer while their parents are on an archaeological dig. Agnes is a bit of a helicopter-aunt. Sophie tells us, "If we are even five minutes late, she gets in a tizzy. Last week, when the trolley car broke down and we were an hour late, she'd already phoned our parents by the time we got there" (5.9).
As annoying as her constant fussing may seem, she's definitely more present in the twins' lives than their parents. The twins care enough about her to explain why they won't be home for dinner so she doesn't worry. Oh and if you're up for more Aunt Agnes, see quotes on the theme of "Family" for more.