Blood Sisters (Katie Maguire Series #5)

In a nursing home outside Cork, an elderly nun lies dead. She has been suffocated. It looks like a mercy-killing—until another sister from the same convent is found murdered, floating in the Glashaboy river. Why would anyone want to kill them? When a child's skull is unearthed in the convent garden, Katie Maguire discovers a 50 year old secret that might lead her to the killer, if the killer doesn't find her first.