Struggling to come to terms with the suicide of her teenage son, Ellie lives in the shadows of the Forth Road Bridge, lingering on its footpaths and swimming in the waters below. One day she talks down another suicidal teenager, Sam, and sees for herself a shot at redemption, the chance to atone for her son's death. But even with the best intentions, she can't foresee the situation she's falling headlong into --- a troubled family, with some very dark secrets of their own.

As Mark Douglas photographs a pod of whales stranded in the waters off Edinburgh's Portobello Beach, he is called by his son's school: His wife, Lauren, hasn't turned up to collect their son. Calm at first, Mark picks up Nathan and takes him home; but as the hours slowly crawl by, he increasingly starts to worry. We gradually learn some of the painful secrets of the couple's shared past, not least that it isn't the first time Lauren has disappeared. And as Mark struggles to care for his son and shield him from the truth of what's going on, the police seem dangerously short of leads. That is, until a shocking discovery.