The Palace of Lost Memories by C.J. Archer

The king’s magnificent palace was built in a matter of weeks. No one saw the builders and no villagers are allowed beyond the gilded gate – until a noblewoman is poisoned. The local doctor and his daughter, Josie, are allowed to attend her, but Josie soon learns the palace won’t surrender its secrets easily, for not a single resident has a memory from before the palace existed.