WARNING: This article may contain spoilers for Grey's Anatomy season 16 episode 16. Read at your own risk.

Grey's Anatomy season 16 episode 16 is arriving this week on ABC, with the title "Leave a Light On." This will be one of the most important episodes of the series this season, as it will finally address the reason why Justin Chambers' Alex Karev left since this has been a major question. Many were eager to find out what really happened and why he decided not to come back.

Alex's storyline has been a mystery and viewers have been wondering how his story will be wrapped up after his sudden exit last year. Now, it looks like Grey's Anatomy season 16 episode 16 will finally address that matter. It was revealed in the previous episode that he never went to Iowa to see his mother. He's just gone and his whereabouts have been a huge mystery.

The promo of Grey's Anatomy season 16 episode 16 hints how Alex's story will end. The clip teased there'll be some closure as to what happened to him. However, this wouldn't be easy for those left behind, especially for his wife, Jo. Alex stood by Jo through everything she's been through and they also celebrated their vows during the Halloween episode.

So, how will the story end considering that he's in the middle of a big storyline? That question will finally be answered in this week's episode. Viewers should also be prepared as this might be an emotional episode. After all, the series is losing an original cast member. But then, Alex may not appear in this episode, as the series may likely use flashbacks and deleted scenes to tell a story featuring him.

In fact, the promo uses some flashback scenes to bring back memories of Alex and other interns. In the clip, Meredith told Alex: "There were five of us, now it's just you and I... and it can't be just me." The promo also played emotional background music, while showing more flashbacks of Alex spending some time with other doctors.

The synopsis of Grey's Anatomy season 16 episode 16 also notes Meredith Grey and other doctors reflect on the past. It might be weird and sad for all of them, knowing that Alex is not coming back for good. He's been with them, especially with Meredith, for a decade and a half. He has a lot of memories with them, so this would definitely be emotional for everyone.

Grey's Anatomy season 16 episode 16 airs on Thursday night, Mar, 5, on ABC.