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.

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.

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.

Meredith and Catherine continue to disagree, and Meredith confides in Bailey for support. Richard, Winston and Lucas spend the day outside of the hospital, and Blue deals with a relationship from his past. Levi meets the new hospital chaplain.

During a high-stress day at Grey Sloan Memorial, the fates of a patient in critical condition and a helicopter-bound medical team hang in the balance. Teddy and Owen work on their marriage, while Bailey, Blue and Link treat a hospital employee.

Teddy and Owen plan a date night that gets derailed in more ways than one, while Jo struggles to do it all at home. Mika adds more to her plate to make up for taking time off to be with her sister, and Levi is faced with a monumental decision.

Meredith and Amelia prepare a funding proposal for their Alzheimer’s research. Meanwhile, Teddy and Owen hit a breaking point in their marriage, while Jules has an awkward encounter with Dr. Beltran.

Amelia undertakes a high-risk brain surgery on a young patient, while Winston and Jules disagree over how to handle their trauma patient's family. Jo and Link struggle with wedding planning.

While the interns are excited to transition to second-year residency, an ordinary day at Grey Sloan takes an unexpected turn when a medical emergency unfolds in the operating room, endangering lives inside the hospital.