A taut and pacy thriller; the start of a stylish new series from an acclaimed writer for teens

Rose and Joshua meet when Joshua and his dad come to live with Rose and her mum. Then their world is shattered when their mother and father go out one evening and never return. With police inquiries going nowhere, Rose and Joshua are separated and sent to live with relatives. Then Rose is witness to not one, but two murders. Why is this happening?

And how does it fit in with the disappearance of their parents?