当洛杉矶出现一个巨大的天坑时，哈里斯一家一分为二。夏娃和她的儿子被送到了一个神秘的原始世界。加文发现困扰他多年的异象可能是将它们带回家的关键

乔希的生命危在旦夕，伊芙穿越危险的荒野回到空地救他。 迫切需要启动救援任务的加文和伊兹努力证明在政府特工追踪他们的一举一动时，天坑内还有幸存者。

随着幸存者的食物供应逐渐减少，伊芙和泰冒险进入森林进行冒险的狩猎探险，结果却面临威胁他们生存的意想不到的危险。 随着一场不太可能的救援任务取得成功，加文必须将他的信仰——以及他家人的命运——交到一位有着复杂过去的老朋友手中。

当夏娃和其他幸存者寻找坠落的飞行员时，一架坠毁的飞机的景象在空地上传播了一股意想不到的希望。 在政府永久暂停他们进入天坑的任务后，Gavin 和 Izzy 从一个不太可能的来源寻求帮助。

Eve、Levi 和搜索队的其他成员探索了一个神秘的堡垒，这个堡垒提出的问题多于答案。 在新盟友的帮助下，加文和伊兹开始了一项危险且未经授权的任务，以拯救他们的家人，尽管政府警告他们可能会造成前所未有的灾难。

随着时间在他们家窗户关闭之前所剩无几，天坑的幸存者进行了最后的逃生尝试。 然而，当他们收到加文的严厉警告，他们的计划将以灾难告终并迫使夏娃做出不可能的选择时，该计划受到了质疑。

当一场混乱的超级风暴袭击空地时，结构性倒塌使玛丽贝斯和卢卡斯的生命处于危险之中。 夏娃仍然与每个人意见不合，她试图通过领导将他们挖出来的努力来弥补。 加文开始了他的过去之旅。

随着寒冷天气的临近，夏娃、利维和泰回到堡垒，尽管他们在那里有过濒死的经历，但希望能了解公元前 10,000 年。生存技能。 Gavin 试图让 Izzy 免于痛苦，这威胁到了他们的关系

当一个惊人的发现让乔什和伊兹的生命危在旦夕时，伊芙和其他幸存者拼命寻找掌握着拯救他们的钥匙的小男孩。 Gavin 和 Izzy 必须依靠陌生人才能让他们的家人团聚。

With news of one last sinkhole opening, Gavin, Izzy and Dr. Nathan race to Seattle to launch a final rescue effort before it's too late. Eve embarks on a perilous journey to send a young boy though a portal in order to save her family.

Desperate to reunite with her son, Eve follows a lead that brings her face-to-face with a ruthless prehistoric group. Gavin, Izzy and Ella question whether they’re fit to survive in 10,000 BC. Josh and Riley wake up in an unfamiliar time.

当加文寻求祖父的帮助引导他找到失踪的妻子时，夏娃和利威尔在一个可怕的新现实中航行。1988年，乔希和莱利发现他们被一个可疑的男人跟踪，他透露了有关天坑背后谜团的信息。

After an emotional reunion, Gavin and Eve attempt a daring escape from their unforgiving captors; Lucas leads a dangerous mission to the fort to reclaim the resources his friends so desperately need.

When a fog falls over the Clearing, Eve leads a defense against a group of invaders, only to encounter a threat more dangerous than they’ve faced before. In 1988, Josh and Riley pursue a woman who may hold the key to stopping the impending tidal wave disaster.

Eve, Gavin and others attempt to commandeer a shipment of black rock to gain access to the mysterious Building, where they believe they may find a way to bring Josh and Riley home. In 1988, Josh and Riley must act swiftly to prevent Caroline from altering the timeline.

When their plan to infiltrate the Building goes awry, Gavin finds himself face-to-face with its enigmatic leader. Eve, Levi, Sam and Izzy are forced to rely on a former adversary to lead a rescue attempt. In 1988, Josh and Riley enjoy some fun before a startling turn.

A reunited Harris family leads the effort to rescue Caroline and stop the sinkholes from happening, only to face forces that threaten to tear their family apart. With Lucas' life on the line, Ty accepts a challenge to win his friend a cure.

The Harrises return to 10,000 BC, determined to upload a virus that will stop all sinkholes, despite knowing that this will mean they will never get home again. An unlikely leader rallies the Clearing to face an oncoming prehistoric threat.

When a Survivor is murdered, Lucas and Sam lead a contentious investigation to find the killer. Gavin embarks on a mission to save Eve from the fateful vision he’s had of her death. Eve finds herself closer than ever to seeing it come true.

A ruthless enemy holds the Clearing captive, threatening to kill a beloved Survivor if their demands for an unexpected item aren't met. Gavin and Sam lead the rescue attempt, aided by an old friend whose return holds more questions than answers.

When the Clearing and Fort unite to celebrate the union of Ty and Paara, the invitation of a controversial guest threatens to upend the festivities. Lucas offers Veronica an unexpected strategy to unravel her captor's odd connection to 10,000 BC.

Eve and Gavin ally with James to infiltrate the Lazarus Building in hopes of saving Ty and stopping Kiera from destroying their only way home. When a deadly horde awakens beneath the Clearing, Veronica must save Ella before a lethal sting kills her.

Gavin leads his family toward a new way home, but each step inches everyone closer toward his devastating vision of Eve's death. Levi, ostracized from the others, is given a chance at redemption when an old foe proposes a deal.

With Gavin on the verge of dying, Eve and her family make a desperate attempt to set things right … even as an unexpected twist threatens to tear them apart forever. Veronica reveals a secret that sends her relationship with Lucas into jeopardy.

Gavin leads the survivors in trying to find Eve, Josh and Riley. Will he be able to finally reunite his family and still find a way back to the lives they once knew?