六年前，美国太空总署观测到地外文明，但是派出勘测的飞船返航时在墨西哥坠毁。从此之后，墨西哥许多地区受到外星神秘生物的感染，无数百姓丧生。美国方面派出军队与巨大的外星怪兽作战，彼此伤亡惨重。 　　洛杉矶的记者安德烈·卡特（斯科特·麦格纳瑞 Scoot McNairy 饰）接受 某富翁的请求，前往墨西哥感染区寻找其女儿萨曼莎·温登（惠特尼·阿贝勒 Whitney Able 饰）。安德烈顺利见到萨曼莎，二人随即踏上开往美国的列车，然而列车却在中途折返。他们被迫寻找其他归国的途径，只是命运难测，回国之路似乎充满险阻。万般无奈，安德烈和萨曼莎只得步行穿越危险重重的感染区……Six years ago NASA discovered the possibility of alien life within our solar system. A probe was launched to collect samples, but crashed upon re-entry over North America. Soon after, new life forms began to appear and half of Mexico was quarantined as an INFECTED ZONE. Today, the American and Mexican military still struggle to contain "the creatures"...... Our story begins when a US journalist agrees to escort a shaken tourist through the infected zone in Mexico to the safety of the US border.