Saundra breaks in to the flashback to ask if Cathy had pain in her chest or on her chest. Cristina says that it was the burns on her chest, but when Saundra thanks and dismisses her, Cristina gets defensive, wondering if they think Cathy had chest pains and she gave the wrong medication. Richard tells her it's hard to say as the next note on the chart is Lexie giving Cathy a chest tube, but Saundra then pretty firmly cuts him off and dismisses her again.
Lexie tells the Three that she was supposed to be with Evan, but we flash back to see how she came to give Cathy a chest tube. She's in the room with Evan when Callie and Mark make their announcements and then when Mark comes back in, he tells Evan gently that he has to cut into the burn to restore the circulation in his arm. Again, this scene is positively devoid of any humor or levity -- it sounds hellacious. Evan, crying, asks about his dad again and Arizona promises they are finding him. She then tries to ask him about his college search -- the reason he is in town -- and Evan says in a small voice he's not sure he could take the rain in Seattle. Just then, Mark starts to cut and Evan lets out an unholy wail. Mark clearly feels horrible and keeps saying he's sorry, assuring Evan he's going to be okay. Arizona tries to stay upbeat and talks about the rain and how it's not that bad, but when she asks Lexie for backup, the normally perky resident is sobbing in the corner and can't answer. Arizona tells her sternly to leave and come back when she's collected herself. Out in the ER, Lexie gulps at the air when Danny (not the best child actor this show has ever seen, but a super cute little boy) tells her she can't breathe. Lexie thinks he's talking about her and assures him that she's okay, but Danny actually means his mom can't breathe. When Lexie pulls back the curtain, we see the same purple-lipped shot of Cathy gasping for breath.
Lexie reports that Cathy had a pneumothorax (collapsed lung) and back in the ER, she's got an oxygen mask on the patient while she holds a giant needle over her. Cathy gasps at her not to let Danny see her die, but Lexie promises that she's not going to die, and starts counting Cathy's ribs on her side. Richard keeps interrupting Lexie's storytelling which creates the same kind of tense, distracted atmosphere that was going on in the ER at the time, when Avery interrupted what Lexie was doing. She loses count (she has to go in through a particular space or could puncture Cathy's diaphragm) because Avery walks up and dramatically plunges something into Cathy's chest and she gasps for air.