Twenty years ago, Kate Maddox was a volunteer at a research unit where scientists experimented to find a cure for the common cold. That summer, Kate fell in love with a handsome young doctor, Stephen. But her stay at the unit ended in Stephen's tragic death and Kate fled a new life in the US. Now, Kate is back in England and on the run again with her young son - this time, from her cruel husband. But a chance encounter with Stephen's twin brother, Paul, sets her on a terrifying path of discovery. What really happened at the Cold Research Unit two decades ago?