The Last Will at Thornmere. Margot Fenn Mysteries, #3

At ten o'clock tomorrow morning, Gideon Thorne will sign a new will. By dawn he is dead in his bed, his old heart, everyone agrees, at the end of a long summer. Everyone agrees too quickly. The Thornes have spent four generations arranging how things look. So when the patriarch dies on the eve of rewriting everything, the family closes around the tidiest suspect: the much-younger second wife, the gold-digger, the woman who was, conveniently, in charge of his medication.
Detective Sergeant Margot Fenn keeps asking the question the house was built to prevent, not who wanted the old man dead, everyone did, but who could not afford to let the sun come up. The answer is in a nurse's handwritten log, a foxglove stem cut from the west border, and the one thing the new will makes plain. For fans of Louise Penny, Kate Atkinson, and Anthony Horowitz. It's never the obvious one, and the truth was in plain sight, seen by someone nobody bothered to ask.