As the worst storm of the century breaks across the North West, sweeping through Snowdonia and across the Mersey to burst upon Liverpool, two women, Molly and Ellen, give birth to girls in a Liverpool maternity hospital. Molly lives on a hill farm in Snowdonia while Ellen is married to Sam O'Mara, a dock worker who is quicker with a punch than a kiss. After one punch too many, Ellen throws her husband out, and eventually leaves Liverpool to live with Molly.
Ellen and her daughter throw themselves into their new life with enthusiasm, unaware that they are being watched by someone hiding in a ruined cottage. And as another horrendous storm breaks across the hills, the watcher makes his move.