A freak tidal surge hitting a Welsh seaside town leaves devastation and three locals drowned. Yet when a fourth body is found in the debris it takes time for it to be identified as the respected Oxford writer Sara Meredith. A celebrity, an icon to an entire generation - what was she doing in such an unlikely place? And how had it ended in her death?

These mysteries overwhelm the lives of people Sara has left behind: estranged husband Josh, their volatile teenage daughter Eurwen and someone else - a stranger. Is this stranger now the only person who can reconstruct Sara's last few weeks, frame-by-frame?