When a raging storm coincides with high seas it unleashes a colossal tidal surge, which travel mercilessly down England’s East Coast and into the Thames Estuary. Overwhelming the Barrier, torrents of water pour into the city. The lives of millions of Londoners are at stake. Top marine engineers and barrier experts Rob (Robert Carlyle), his ex-wife Sam (Jessalyn Gilsig) and his father Leonard Morrison (Tom Courtnay), have only a few hours to save the city from total devastation.