في الفلاش باك ، قبل سبعة وتسعين عامًا ، تعمل بيكا ومساعدها بيري جوردون على الإصدار الثاني من ALIE إنه في شكل شريحة ذات ملاحق تشبه اللوامس ، لكنها تتعطل باستمرار. فجأة حصلوا على إرسال من كريس . يحذرها من أن ALIE قد خرجت وهي على الشبكة. أنها تقوم باختراق رموز الإطلاق النووي. يسأل بيري لماذا ، ويجيب بيكا مع مشكلة ALIE المفترضة مع الإنسانية: "الكثير من الناس".

تخبر بيكا كريس أن يرسل فيروس حبوب منع الحمل المسمومة الخاص بـ ALIE ويقتلها. يحذرها كريس من أنه قد فعل ذلك بالفعل وقد حجبته عن كل شيء. وأمر باللجوء إلى ملجأ المنارة الخاص بهم. يدخل قائد Polaris ، كول ماك آدامز ، إلى المختبر وينبههم إلى أن سبعة وعشرين صاروخًا باليستي عابر للقارات قد تم إطلاقها من الصين وتستهدف الولايات المتحدة.

من محطتهم الفضائية ، Polaris ، يشاهدون في رعب بينما تقترب الصواريخ من وجهتها. تمكن McAdams من الاتصال بزوجته وابنته ، لكن الإشارة ضاعت. تتواصل الصواريخ القادمة من الصين ، وتعود الولايات المتحدة إلى النيران. تسقط القنابل النووية على كل مدينة رئيسية تقريبًا ، وتُترك الأرض تغلي في الإشعاع.

مرة أخرى في عام 2150 ، تحتفل Lexa و Nightbloods بيوم الصعود. فجأة ، دخلت سيميت غرفة عرشها. لديه أسير أوكتافيا ، ويدعي أن سكيكرو دمر قريته. يتوسل من قائده أن ينتقم لهم ويقتل كل سكيكرو. كلارك ، ليكسا ، وتيتوس يناقشون الوضع. يريد تيتوس من ليكسا تدمير العشيرة الثالثة عشرة كإظهار للقوة. بينما يريد كلارك أن يقوم سكاي بيبول بإسقاط بايك بأنفسهم.

في نهاية المناقشة ، قررت ليكسا دعوة جيوش العشائر الاثني عشر والتقدم في مسيرة إلى أركاديا ، ليس لمهاجمتهم ولكن لحصارهم والسماح لسكيكرو بإخراج قادتهم من الداخل. ومع ذلك ، فإن أي Skaikru يتم العثور عليه بعد المنطقة العازلة التي يبلغ طولها خمسة أميال سيخضع لأمر قتل. يحاول سيميت اغتيالها بدافع الغضب ، لكن تيتوس يعدمه أولاً. مرة أخرى ، أخبر ليكسا أن الدم يجب أن يحتوي على دم.

في الضريح ، يحرر مورفي نفسه من قيوده ويحاول الهرب. ومع ذلك ، الباب مغلق. استعدادًا للدفاع عن نفسه ، يسرق مورفي رمحًا من الكبسولة ، مما يتسبب في إغلاق الباب حيث يقرأ بوليس ، اسم العاصمة. إنه يرى أن هناك فجوة بين "بول" و "هو" ، والتي تم استبعادها. أدرك مورفي ، بعد تحليل لوحات الكهوف على الجدران ، أنه قرأ بولاريس ذات مرة.

In a flashback of 2054, two years after the world ended, Becca is seen injecting herself with a black fluid, altering her DNA and rendering her blood a black color. In her briefcase, it is seen that there are many more vials of the black fluid. McAdams confronts Becca, having been told by her assistant, Peri, that Becca's artificial intelligence program was what destroyed the human species. The commander is preparing to dock along with the other twelve stations, to create the Ark, and angrily tells her it is being designed to ride out the nightmare that Becca created.

They will not join the Ark, which is scheduled to unite in two hours until the second A.I. is floated. Becca pleads that the A.L.I.E. 2.0 is exactly what they will need, what will save them on the Ark. She fears that the Ark will not survive with limited normal human scientists doing the calculations and that the A.I. will help them survive because A.L.I.E. 2.0 will have a biologically-based human conscience that will know humanity's "wants and needs" because it will also want and need the same things that humans will. However, the Commander is not convinced and goes with Peri to find something to float the research in. Becca, guilt-ridden and in need to make some amends for the destruction she caused, is still convinced that A.L.I.E. 2.0 will help the remains of humanity to survive and locks herself in the lab.

Back in Polis, Clarke is faced with two choices: return with Octavia to stay imprisoned inside Arkadia until Pike is defeated, or remain in Polis with Lexa, who still has feelings for her. Titus is against the latter and warns her that Clarke may become like Costia. This enrages Lexa and reassures him that she is more than capable of separating feelings from duty. He apologizes, and she says that it is Clarke's decision on whether she wants to leave or stay.

Octavia finds Indra in the capital, and attempts to convince her to come back to help them battle the Arkadians. Indra feels as if her honor has been lost, and displays this when even Octavia proves to be superior to her in combat. However while Octavia waits impatiently for Clarke to join her, Indra appears and they head back to Trikru without Clarke.

Titus returns to the shrine where Murphy is waiting to attack. Titus defeats Murphy and is on the verge of killing him when Murphy begins to explain what the shrine actually is. He tells him about the end of the world, the nuclear radiation, and why Skaikru needed to stay in space. Murphy explains that Polaris was the thirteenth station and that the woman in the cave paintings must have escaped and landed on Earth, and was just like The 100. Titus, while doubtful, says that Becca is nothing like Skaikru and knocks him out.

In another flashback, McAdams warns Becca that the other stations are threatening to stop docking maneuvers because Polaris has not started. Alpha Station contacts Polaris and threatens to martyr them. Becca launches from the pod, wearing the commander's spacesuit. The Alpha Station destroys Polaris to send a message to the other stations and forces them to join, threatening that the same thing will happen to the other federation stations if they choose not to join.

Clarke, who has decided to leave, says goodbye to Lexa. She hopes that one day, they will owe nothing more to each other's people and will be able to live peacefully. Lexa hopes they will meet again. Before she leaves, Clarke and Lexa have sex. Afterward, Clarke examines a tattoo on Lexa's back. She explains that she got it on her Ascension Day, and each circle represents each Nightbleeder who died. There were nine participants in Lexa's conclave, but only seven circles on her back. Clarke asks what happened to Number Eight, but Lexa says she does not want to talk about it, and they begin to kiss again.

As Clarke prepares to leave with Octavia, she finds Murphy outside Lexa's sleeping quarters. He is tied up and injured, but alive. Titus pulls out a gun, saying if he kills Clarke with a Skaikru weapon, Lexa will think it was Murphy and may be so heartbroken that she will declare war and kill the Arkadians. Clarke manages to dodge the bullets, but Titus, who is not skilled with firearms, accidentally fires a stray bullet, which hits Lexa in the stomach.

Titus realizes what he has done and helps Clarke put Lexa on the bed so she can save her. She begins losing too much blood, but Lexa tries to calm Clarke and tells her not to be afraid. Titus prepares to retrieve her spirit and begs for forgiveness. Lexa simply haves him swear that Titus will never attempt to harm Clarke again, which he swears. She then tells him to do his job and serve the next commander as he served her. Clarke tries desperately to save her. Lexa is convinced that her spirit will find a new Nightblood, but Clarke only wants Lexa and not another commander.

Lexa tells Titus that she is ready, and tells Clarke that her fight is over. She also manages to tell Clarke that life is about more than just surviving. Clarke then recites the traveler's blessing to her and kisses Lexa for the last time. Lexa dies shortly after. After convincing an incredibly saddened Clarke that he must complete the ritual. He turns Lexa over on her back, where above her Ascension Day tattoo, across the nape of her neck, is the same infinity symbol that Titus was interrogating Murphy about, and the same symbol on Jaha's pills.

Vertically down the center is a scar, which Titus reopens. As blood pours out, A.L.I.E. 2.0, now sentient, emerges. Titus puts it into the sleep mode and stores it away in an old tin box. He carries away Lexa's body and alerts the Grounders that the conclave must begin and that Lexa is dead. Her spirit (the A.I. plucked from her nape) will choose the next commander. They lock Clarke and Murphy inside her chamber, and Murphy attempts to break free while Clarke stares at the black blood stains on the bed in shock.

نجت بيكا وتهبط على الأرض ، في أنقاض بالتيمور خلال الشتاء النووي. كسرت بدلتها وارتفعت مستويات الإشعاع. يُفترض أن السائل الأسود الذي تم حقنه يقاوم آثار الإشعاع النووي حيث تمكنت من خلع خوذتها والتنفس بأمان. من بين الحطام ، ترى بيكا أن البشر يقتربون من بعيد ، يرتدون بدلات واقية. تخبرهم أنها هنا للمساعدة. من المفترض أنها ستحقن هؤلاء الناجين بالسائل الأسود وتجعلهم محصنين ضد الإشعاع أيضًا. من الواضح أن على مؤخر بيكا ، المخيط بشكل فظ ، هو نفس القطع الرأسي الذي يجب أن يحتوي على نفس الذكاء الاصطناعي