DeLuca can’t figure out what’s going on with his incurable patient Suzanne and he turns to a diagnostics genius, Dr. Riley from UCSF, for help. Bailey checks in on Joey, a foster kid that Ben brought into Grey Sloan. Meanwhile, Amelia is getting the results of her paternity test and Jo confronts her about how she is treating Link.

DeLuca is irritated after Meredith takes over his patient Suzanne whose symptoms continue to stump the doctors at Grey Sloan. Elsewhere in the hospital, Jackson, Owen and Jo work on a couple injured in a bear attack; and Levi is hurt when Nico doesn’t want him to meet his parents.

Meredith and Carina question DeLuca’s uncharacteristic behavior when he volunteers to perform a life-threatening task during a blizzard. Meanwhile, Bailey tries to help Joey with his future, while Richard trains a new intern at the hospital.

Link tries to convince Amelia to take it easy during the final stage of her pregnancy. Hayes asks Meredith a surprising question, and Owen makes a shocking discovery.

The doctors of Grey Sloan Memorial must contend with the COVID-19 pandemic; an unintentionally started fire has first responders from Station 19 bringing patients into the hospital for treatment.

The Grey Sloan doctors continue to face their new COVID-19 reality and deal with a familiar and stubborn patient. Koracick is put in charge of the interns who recently joined the hospital ranks and Link operates on a sex therapist. Elsewhere, Maggie finds comfort in Winston's virtual presence.

Owen faces a medical diagnosis that challenges more than he imagined. Meanwhile, Koracick begins to go stir crazy; and Maggie gets a not-so-subtle glimpse into Winston's background.

Maggie is preoccupied with Winston while trying to treat a patient wounded in the Seattle protests. Meanwhile, Levi is tested by an emergency, and the doctors struggle to treat a patient who doesn't believe in COVID.

Meredith seeks advice from Amelia. Meanwhile, Richard is reenergized as he takes teaching to a new level at the hospital, and Winston treats a patient suffering from kidney failure.

Seattle’s favorite redhead returns and graces the Grey Sloan halls with her experience and expertise as she attempts to help Richard teach the newest crop of residents. Meanwhile, Meredith has a decision to make, and Link confides in Teddy.

Richard recruits Meredith and Bailey to help him launch a new program. Meanwhile, Addison’s patient has complications from a procedure, and Jo helps a woman who goes into premature labor.

The Grey Sloan doctors spring into action after an explosion rocks Seattle, with the incoming trauma hitting close to home. Owen experiences PTSD after he hears the explosion, while his sister Megan enlists help from Winston and Hayes in confidence. In Minnesota, Meredith and Amelia meet up with a familiar face who assists in their study.

The crossover starts on Station 19 S05E05 Things We Lost in the Fire (I).

Dr. Hamilton takes his frustrations out on Meredith, so Nick gives her a chance to blow off steam by scrubbing in on a surgery. Back in Seattle, Link and Jo take their kids to a fairytale theater performance that goes wrong. Bailey and Dr. Lin attend a recruitment fair in hopes of attracting more doctors to Grey Sloan but find themselves ill-prepared.

The doctors celebrate the holidays; Hamilton and Meredith prepare for a milestone on their project; Link wants to spend the holiday with Amelia and Scout as a family; Schmitt is faced with a difficult decision during surgery.

Schmitt must face the Morbidity and Mortality conference. Meanwhile, Meredith convinces Nick to scrub in on a surgery in Seattle, and Jo faces her feelings.

While Meredith, Amelia and the team prepare for Dr. Hamilton’s long-awaited, groundbreaking surgery, Bailey receives an unexpected offer. Owen’s impatience makes him a difficult physical therapy patient, forcing Link to intervene. In Minnesota, Nick makes a liver transplant a teaching moment.

While Richard ponders his surgical abilities, Jo is charmed by her patient’s brother. Elsewhere, Megan makes sure Teddy and Owen talk out their differences, and a pet python causes an uproar.

Tensions at Grey Sloan Memorial rise as the effects of the physician shortage begin to show. Meanwhile, Meredith struggles to step away from work as she spends a sick day at home with Zola, and the hospital receives an unexpected visitor.

Bailey is on edge when an accreditation council stops by Grey Sloan to review the residency program, while Richard sets an assessment of his own for the same day. Meanwhile, Nick returns to Seattle to perform a first-of-its-kind operation with Meredith.

A dinner party is thrown at the sister house in Nick's honor. Meanwhile, Grey Sloan Memorial receives a victim of a brutal hate crime.

Due to a blood shortage, Grey Sloan Memorial is setting up a voluntary donation center. Meanwhile, Nick asks Meredith for help with his patient and Winston is hung up on his relationship with his brother.

The blood shortage at Grey Sloan Memorial continues. Meanwhile, Meredith makes a risky decision regarding a patient, and Owen’s actions to help his fellow veterans come to light.