一对喜欢冒险的夫妇说服他们的朋友去探索澳大利亚北部森林中一个从未有人踏入的洞穴系统。忽然暴风雨来临，大家决定进入地下洞穴避难。不想洪水冲进了洞穴，氧气含量逐渐下降，大家被困在了一个完全未知的环境里。他们没有料到的是，潮湿的空气和不断上升的水位只是这次旅程最小的挑战，洪水还带来了最危险的捕食者：一群危险又饥饿的鳄鱼。当危险逐渐升温，这群朋友之间彼此隐瞒的秘密渐渐被揭开，他们争吵打斗、彼此背叛，只为在这个险境中生存下来。
17岁初中毕业便辍学在家的臭妮是个标准的问题少女，脾气暴躁，且调皮，母亲一人靠打鱼养活她。臭妮20岁这年，在一次聚会中臭妮无意中扎伤富二代陈小富。同时母亲在打鱼过程中遭鲨鱼袭击遇难，在医院抢救。在陈小富的追责中臭妮，深夜拿着父亲的照片离开小岛，踏上了寻父之路。
魏佳欢生日这天，父亲魏成功陪她登上环海游艇，然而一场突如其来的海难打破了一切，整艘游艇侧翻，众人纷纷落水。魏成功自哭喊声中醒来，发现自己身处一荒岛，目睹魏佳欢被一巨蛇叼走，于是随众人深入丛林，踏上营救之路。在这片与世隔绝的丛林里，无数怪异的史前生物暗藏其中，营救女儿的遥遥之途布满杀机。另一边，魏佳欢等人在蛇穴中醒来，在失去规则的封闭环境中，幸存者的人性也承受着巨大考验…
John Wood left the pieces of a broken civilisation behind, to go back to his roots in the woodland, after a virus pandemic struck the world. Residing in a simple cabin, he only wants peace and to live in harmony with nature. Coming from a long line of timber men, he joined the army and served as a soldier for many years. Rebelling against his superiors for killing civilians under martial law. John feels he got his own wife killed when saving hundreds of innocent civilians from certain death. His wife executed point blank as retribution for John's disobedience and supposed heroic acts. Now, a young woman named Maria Johnson has escaped a pandemic research lab. She's been part of experiments to find a cure for the still raging virus. Carrying the potential cure in her blood, she is hunted by profiteers and mercenaries who knows her secret. Coming upon John's cabin in the woods, Maria is instinctively taken into shelter by John. He wants her to recover fast and leave, but by learning her...
