The Secret Keeper, by Kate Morton

Kate Morton does history, love, and family with humor, insight, and suspense.  Laurel Nicholson is a very successful actress, who joins her siblings at the deathbed of their mother, Dorothy.  With the help of her brother, Gerald, she tries to get to the bottom of a violent episode she witnessed as a young teen. The violence stems from a period in Dorothy's life when she was an ambitious lady's maid and her friends Vivien and Jimmy fall in love while helping at a children's hospital in war torn London.