An ambitious young executive is sent to retrieve his company's CEO from an idyllic but mysterious "wellness center" at a remote location in the Swiss Alps, but soon suspects that the spa's treatments are not what they seem.

In a room with no windows on the eastern coast of Africa, a Scotsman, James More, is held captive by jihadist fighters. Thousands of miles away in the Greenland Sea, Danielle Flinders prepares to dive in a submersible to the ocean floor. In their confines they are drawn back to the Christmas of the previous year, where a chance encounter on a beach in France led to an intense and enduring romance.