Casey, Jane (Jane E.). Maeve Kerrigan series

Every mother's worst nightmare... When nine-year-old Rosalie Marshall vanished from her bed one summer night, her disappearance tore her family apart. Now, sixteen years later, her mother Helena is found dead, her husband by her side. It looks like a straightforward murder-suicide but DS Maeve Kerrigan and DI Josh Derwent soon discover nothing about this case is straightforward. The Marshalls have been keeping secrets, and they aren't alone. Josh has been holding something back too - something that could change everything for Maeve. But one person is prepared to kill to hide the truth. Until Maeve finds out what happened to Rosalie, no one will be safe