The first we see of Mark is the rescuers looking at the makeshift bandages on his chest, wondering what the others did to him out in the forest as if they just carved him up to pass the time. There's a quick flash to Lexie's death and then Mark opens his eyes a sliver, now on the plane back to Seattle. He sees the body bag on the gurney next to him and proceeds to try to die again. Even once he is back in the hospital, they still have to shock him at least once to get his heart beating.
Julia is frantic at his bedside in Seattle and tells him that she flew to Boise but they refused to let her see him since she wasn't family. In a raspy voice, he chokes out that she deserves better. She's confused, and tells him she's here now and not leaving. "I love you!" He sighs and then replies, "I love Lexie. Loved. I'm sorry." Her face crumbles, and I can't help but feel for her. I always wanted him to be with Lexie but as someone who has been dumped for someone else, I can say with authority that it sucks balls. I did actually wonder during the finale if they were going to show a scene like this (if Mark lived to make it back to Seattle) and am glad they gave that character some closure.
Derek finds Callie sleeping next to Mark's bed and tells her in a whisper to go home, but she refuses even though he points out that she's a zombie from keeping vigil at both Arizona's and Mark's bedsides. She mumbles that she just needs coffee but Derek tells her that he'll stay with Mark all night so she can get some rest. She admits that she's afraid that Mark is giving up and they are losing him. When Derek tells her that won't happen, she makes him promise and he does, joking that Mark idolizes him and will do whatever he says. I think by the end of this episode we should all agree that while it's good to make loved ones feel better and to give them hope, making promises about grave medical situations over which they have no real control is usually a really bad idea. Derek does seem to get this and after Callie leaves he tells Mark he's not allowed to make Derek look like an ass by dying and making him break his promise.