梅莉迪絲依然擔任臨時外科主任。此前她拒絕了尼克提出的搬到明尼蘇達州的建議後，如今再次見到了尼克。貝莉告訴理查她還沒有準備好重返工作崗位。李維鼓起勇氣向喬透露了令人失望的消息。

一位大學生被送到了醫院。乍看像是食物中毒，但病人的病情不斷加劇，而且伴有可怕的併發症。外科主治醫生和實習生合作解決醫學難題。喬在休息日和貝莉待在一起。

貝莉召集實習生製作一系列關於青少年性教育的公益廣告，向青少年普及性健康知識。這些影片是在葛蕾·斯隆紀念醫院當著一群高中生的面拍攝的。一名學生在參觀醫院期間出現了併發症，這些影片恰巧派上用場。梅莉迪絲和瑪姬知道了關於左拉的近況。

葛蕾·斯隆紀念醫院慶祝萬聖節之夜。梅莉迪絲和尼克獨處。李維由於過度勞累感到身心俱疲。溫斯頓和歐文要求實習生在真正的屍體上進行急診外傷訓練。

貝莉和艾蒂森前往一個家庭計劃中心做志工。一位宮外孕病人出現了併發症。實習生們調查盧卡斯與艾美莉雅的關係。梅莉迪絲在前往波士頓的途中與傑克遜相遇。

一條爆炸性的新聞出現後，緊接著一場雷雨襲擊了葛蕾·斯隆紀念醫院。外科主治醫師和實習生共同努力，搶救一名受傷的記者和受風暴影響的家庭。一位受人愛戴的作家接受高風險手術。

梅莉迪絲在格雷斯隆紀念醫院的最後一天，醫院裡的醫生計畫為她開一場驚喜歡送會，尼克當面質問她兩人的感情有沒有未來；實習生爭相參與一場空前的手術；理查問泰迪一個重要問題。

泰迪做出了一個艱難決定；麥琪和溫斯頓出現矛盾；在為一位知名運動員進行手術前，林克向喬尋求情感援助；一位不速之客讓西蒙娜和盧卡斯震驚不已。

一位故人再次出現，西蒙娜需做出重大決定。麥琪進行一場高風險的手術，布魯和朱爾斯在一旁觀摩學習。喬和林克救治一位孕婦。盧卡斯和米卡舉辦了一場驚喜滿滿的派對。

盧卡斯和布魯在進行一例手術時遭遇難題，凱瑟琳回到葛蕾斯隆醫院幫忙救場；阿米莉亞治療一名可能患了癌症的患者，其家人有點支持過頭；歐文打算親自拯救自己的醫療事業，這令泰迪頗為吃驚。

艾蒂森作為特邀嘉賓探訪了葛蕾斯隆醫院，歡迎貝莉的婦產科新學員；瑪姬的肺移植手術出了亂子；在這一天發生令人震驚的轉折之前，尼克與盧卡斯增進了彼此之間的感情。

在診所發生令人震驚的事件後，醫院立即進入封鎖狀態，葛蕾斯隆醫院的醫生分頭行動，拯救多人的性命；瑪姬和溫斯頓鬧矛盾；朱爾斯的室友突然現身。

一名身受重傷的公牛騎士出現在葛蕾斯隆醫院，迫使瑪姬、艾美莉雅、歐文和布魯審視自己的偏見；席夢妮找不到人當自己的伴娘；米卡採取過激舉動來償還她的就學貸款。

瑪姬的最後一天；艾美莉雅與凱的關係受到考驗；貝利遭到人肉搜尋，情況愈演愈烈，班很擔憂。

在李維的幫助下，一位患者慶祝一個里程碑；喬處理一例有難度的診斷；瑪姬和溫斯頓決定自己該何去何從。

艾美莉雅因個人問題對同事發洩情緒；貝利面臨的威脅到了駭人聽聞的地步；盧卡斯和朱爾斯對病人做出了一個冒險的決定；米卡精疲力竭，努力支撐。

泰迪召開緊急會議，討論實習計劃；林克在為一台大型手術做準備時，陷入自我懷疑中；盧卡斯身陷困境，尼克及時給予他指引。

理查德和泰迪宣布一則激動人心的消息；朱爾斯和布魯因照顧麥可馨的事爭論不休；一位藝術家面臨一場高風險手術，他在盧卡斯的幫助下做出決定；喬和米卡照顧山姆；西蒙娜面臨一個改變人生的決定。

Simone's wedding day arrives as Jo and Link's relationship hits a major turning point.

主治外科醫師飛往波士頓，尼克和梅莉迪絲迫不得已重新見面。貝利收穫驚喜。

Meredith rethinks her plans. The interns are on thin ice following a patient's death. Simone and Lucas are immediately tested in an emergency. Richard confides in Bailey. Teddy's fate is revealed.

Bailey tells the interns they must complete dozens of basic procedures before being allowed back in surgery; things are awkward between Simone and Lucas; Amelia comes up with a solution to a complicated surgery.

Meredith and Amelia work to secure funds for their research while Amelia finds herself at odds with a new attending. Levi runs into someone from his past, and Owen gives Winston advice. Lucas ditches Mika, forcing her to treat a patient alone.

Dr. Arizona Robbins returns to Grey Sloan for a particularly complicated case. The interns are interrogated about their past mistakes, while Teddy is eager to return to work after her health scare.

It's all hands on deck at Grey Sloan when a group of medical students is injured by a floor collapsing at their white coat party. Jo and Link are forced to talk about the future, while Jules confronts Winston about his attitude.

Mika and Teddy receive a patient from a nearby penitentiary. Catherine pushes back on Link and Monica's treatment plan for a VIP. Bailey tries to integrate wellness into the residency program.

An unexpectedly complex case brings back painful memories for Simone. Jules and Blue make a high-stakes bet on who can finish their procedure log first. Richard suspects Winston is avoiding him.

Owen and Teddy have the day off but encounter an injured civilian. Monica enlists Amelia's help with an operation on a young patient. The interns complete their procedure logs, allowing them back into the OR.

Just as Amelia comes to a realization, Teddy encourages her and Meredith to speed up their Alzheimer's research over fear of Catherine finding out. Mika finds herself caught in the middle of Link and Jo; meanwhile, Lucas receives bad news.

Wildfires threaten the Seattle region, leading to a flood of patients and emergency procedures. The doctors juggle overcapacity in the ER, complex surgeries and personal stress. Meanwhile, Meredith makes a rash decision that can't be undone.