New Fortress stock plunged in the first half of September but popped 69% in the second. Is its new $4 billion deal a turning point?September was nothing short of a wild roller coaster for investors in New Fortress Energy (NFE -0.81%). The stock nosedived over 45% in the second week of September, only to stage a stunning comeback and soar over 40% in a single day on Sept. 17 after the company negotiated a multibillion-dollar contract.While shares of New Fortress Energy still closed the month of September dow ...