‘Grey’s Anatomy’ Celebrates 400 Episodes — Jackson & April Return in Finale Promo (VIDEO)

Grey’s Anatomy is ending its 18th season with a big event: two episodes, the second of which is the 400th of the series! And to make it even more special, Jesse Williams and Sarah Drew are back as Dr. Jackson Avery and Dr. April Kepner, respectively.

Right from the start, the promo goes back to the ABC medical drama’s roots, giving fans the chance to (very quickly!) relive the love and heartbreak leading up to the milestone. And of course “Chasing Cars” is playing.

Focusing on what’s happening in the present, Grey Sloan is preparing to find out whether or not their residency program can continue, and it looks like that’s at least part of why Jackson is back, if not the only reason. And whatever brings April into the hospital, Dr. Miranda Bailey (Chandra Wilson) is going to be putting her to work when they’re short-staffed. (But April knows where she’s going very well.)

Also in the two-hour event, Dr. Owen Hunt (Kevin McKidd) may be facing some serious trouble if how he’s helped veterans is revealed — and he’s being blackmailed! Plus, there’s the question of whether or not Dr. Meredith Grey (Ellen Pompeo) will truly leave Seattle behind. “Do you want this place to just crumble completely?” Jackson asks her. Watch the promo below for more.

In the first hour, “Out for Blood,” Grey Sloan sets up a voluntary donation center due to a blood shortage. Meanwhile, Dr. Nick Marsh (Scott Speedman) asks Meredith for help with his patient and Dr. Winston Ndugu (Anthony Hill) is hung up on his relationship with his brother.

Then, in the Season 18 finale and 400th episode, “You Are the Blood,” the blood shortage continues. Plus, Meredith makes a risky decision regarding a patient, and Owen’s actions to help his fellow veterans come to light.

Grey’s Anatomy, 2-Hour Season 18 Finale, Thursday, May 26, 8/7c, ABC