The Silence by Susan Allott

Isla comes home to Australia when her father is under suspicion for the disappearance of their neighbor decades ago. Mandy used to care for Isla and although she remembers very little of the time Mandy and her husband were neighbors she can't imagine her father to be anything but innocent. Tensions build as more questions are asked and others, including Isla's mother begin to have doubts.
The chapters alternate between the present and right before the disappearance in the 60's. For fans of dark mysteries from down under like Jane Harper and Candice Fox this is a must.  4 stars