Two friends go on holiday. Only one comes back. Orla and Kate have been best friends forever. Together they've faced it all - be it Orla's struggles as a new mother or Kate's messy divorce. And whatever else happens in their lives, they can always look forward to their annual weekend away. This year, they're off to Lisbon: the perfect flat, the perfect view, the perfect itinerary. And what better way to kick things off in style than with the perfect night out? But when Orla wakes up the next morning, Kate is gone. Brushed off by the police and with only a fuzzy memory of the night's events, Orla is her friend's only hope. As she frantically retraces their steps, Orla makes a series of shattering discoveries that threaten everything she holds dear. Because while Lisbon holds the secret of what happened that night, the truth may lie closer to home…