In this photo from the fourth season finale of Grey's Anatomy, "Freedom," Derek, Mark and Richard are seen in a rare scene outside Seattle Grace. Where is it?

In this photo from the fourth season finale of Grey's Anatomy, "Freedom," Callie and Mark share a moment outside the hospital. What's to come of these two?

In this photo from the fourth season finale of Grey's Anatomy, "Freedom," Callie and Mark have a conversation outside Seattle Grace. What's to come of them?

In this photo from the fourth season finale of Grey's Anatomy, "Freedom," Callie and Mark have a conversation outside Seattle Grace. What's to come of their relationship, if anything?

In this photo from the fourth season finale of Grey's Anatomy, "Freedom," Callie and Mark have a conversation outside Seattle Grace. Will they get together?

In a photo from "Here Comes the Flood," Mark Sloan and Erica Hahn share a conversation while the Chief talks. What could it be about?

In this picture from "Here Comes the Flood," from the fifth season of Grey's Anatomy, Mark and Derek listen as Richard addresses the staff.

It's a new day at Seattle Grace and a new doctor - Owen Hunt - is already shaking things up.

Attendings Mark and Derek smile in a promotional photo from "Life During Wartime," shot for the fifth season of Grey's Anatomy.

Mark and Derek look on in a promotional picture from "Life During Wartime," from the fifth season of Grey's Anatomy. They don't look too sure about these developments, whatever they may be.

Mark Sloan (a.k.a. McSteamy) looks on in a promotional shot from "Rise Up," from the fifth season of Grey's Anatomy.

In what appears to be his final act, Nathan convinces Peter to turn on Adam. After all, he's not a nice guy.