Helen Callaghan

Following their father's death, Cass and her sister Sid will do whatever it takes to keep their family's dive school afloat. It used to be the go-to destination in Cornwall for those keen to explore the ocean's hidden depths. But when Cass returns from a long trip, she's shocked to discover how bad things have become. The business is in decline. Sid's new boyfriend has far too much control over the accounts - and her sister. Then, Cass discovers a body in the water. And as more girls go missing, she wonders just how far someone will go to keep their secrets buried...

On a cold, windswept night, Fiona arrives on a tiny, isolated island in Orkney. She accepted her old friend's invitation with some trepidation - her relationship with Madison has never been plain sailing. But as she approaches Madison's cottage, she sees that the windows are dark. The place has been stripped bare. No one knows where Madison has gone. As Fiona tries to find out where Madison has vanished to, she begins to unravel a web of lies. Madison didn't live the life she claimed to, and now Fiona's own life is in danger...