Brian Murphy and his family are enjoying a relaxing summer excursion in Cape Cod when his wife, Emma, comes down with mild flu-like symptoms. But their leisurely return home to New York City quickly turns into a race to the ER as she begins seizing and falls into a coma. At the hospital, she is diagnosed with Eastern Equine Encephalitis, a rare and highly lethal mosquito-borne viral disease caught during one of their evening cookouts. Worse still, Brian and Emma's young daughter exhibits alarming signs of the same illness.