A bright autumn morning, London shines in all its glory - its architecture, its iconic river and the impressive edifice of the Thames Barrier gleaming in the sunlight. Meanwhile, in Scotland, a storm of hurricane proportions crashes into the coast, devastating the sleepy town of Wick. Mountainous tides barrel mercilessly along the North Coast of Britain, heading for London. However the authorities remain sceptical that nature could deal any blow that London's Thames Barrier, the largest fixed tidal defence in the world, could not withstand. But the reality is that the storm and seasonal high seas will soon converge in the Thames causing a colossal surge, big enough to flood London.
Rob Morrison, (Robert Carlyle) head of Atlantis Engineering, is just back from holiday and he's annoyed to be called to the Thames Barrier for a maintenance check. His ex-wife, Sam, (Jesslyn Gilsig) the Barrier's Director of Operations, is the last person he wants to see. Meanwhile his estranged father, engineering genius Professor Leonard Morrison (Tom Courtenay) is desperately attempting to contact the Barrier high command with a warning about the potential ineffectiveness of the structure. Upon receiving the news that a colleague has drowned during the devastation at Wick and with soaring water levels and a unique set of weather conditions closing in, Rob realises that his father's worst predictions are coming true. Rob, Sam and Leonard must put aside their personal differences to mount an operation to save London from certain destruction.
Timely yet terrifying, FLOOD predicts the unthinkable. When a raging storm coincides with high tide it unleashes a colossal tidal surge, which travels mercilessly down England's East Coast and into the River Thames. Overwhelming the Barrier, torrents of water pour into the city. The lives of
millions of Londoners are at stake. Top marine engineer, Rob and his father Leonard Morrison rush to the aid of his ex-wife and Barrier expert, Sam to try to save a city on the brink of annihilation.