Peggy and Molly Gainsborough—the daughters of one of England’s most famous portrait artists of the 1700s and the frequent subject of his work—are best friends. They spy on their father as he paints, rankle their mother as she manages the household, and run barefoot through the muddy fields that surround their home. But there is another reason they are inseparable: from a young age, Molly periodically experiences bouts of mental confusion, even forgetting who she is, and Peggy instinctively knows she must help cover up her sister’s condition.