As Hurricane Ophelia bears down on New York City, millions are caught up in the horrific flooding it unleashes. Successful interior designer Ellen Wharton flies into New York from London, heedless of the hurricane warnings. She is intent on seeing her mother, Grace. But when the storm hits, the women are forced to wade through freezing waters to the police boats outside. British investment banker Charles Williams is travelling on business but is also eager to see his young daughters, who live with his beautiful, estranged ex-wife. As the hurricane rages, he desperately checks the shelters where thousands have taken refuge to find them, and runs into Ellen and her mother. Meanwhile Juliette Dubois, a dedicated ER doctor, fights to save lives when the generators at the hospital fail. The day of chaos takes its toll as New Yorkers struggle to face a natural disaster of epic proportions.