Two people come into the hospital after getting in an accident presumably while having sex. Jackson, April, Maggie, Andrew, and Stephanie debate how the couple gets into the accident while having sex, coming up with reasons and ways it could have happened. Eliza and Arizona take on a more optimistic view on love while Maggie comes off cynical. The woman is rushed to surgery because she's unconscious. The man keeps worrying about the woman and wants to know where she is and wants to see her.
Stephanie has returned to the hospital after attending therapy three times. Webber gives her the go ahead but Eliza is annoyed that she's back. She's on babysitting duty with the man. When she tries to sneak the guy in the sees the girl after taking pity on him, things get complicated. The woman woke up and revealed that they are not a couple, she tried to kill the man because he was trying to rape her.
Jackson is worried when he figures out that he left Stephanie with the guy. Bailey orders a code orange. The rapist figures out that people are looking for him and holds Stephanie hostage with a scalpel. He tries to get her to find him a way out of the hospital. They pass ben and he doesn't notice that she's in distress. The rapist cuts Stephanie when she tries to break away.
They get trapped in a hallway with Erin, the sister of a patient that was brought into the hospital earlier. Owen saved the parents baby when the baby was choking, and the parents stopped paying attention to Erin who kept wandering around the hospital. Erin was caught by Nathan and Meredith more than once and eventually noticed that the rapist was holding Stephanie hostage. he wanted to take the girl but Stephanie wouldn't let him.
The code orange put the hospital in lockdown so Stephanie told him that he can't leave unless it's an emergency like a fire. Erin, the little girl, helps the rapist start the fire before Stephanie stops her. When he's working on getting the sprinklers to go off, Stephanie douses him with accelerant after telling Erin to look away. She lights him on fire and she and the girl go into another room to hide. Stephanie notices that he's headed towards the oxygen tanks. She opens the door to stop him but its' too late. Everything explodes. The wing of the hospital explodes and Stephanie is thrown back.
Owen gets a knock at the door. Its' two service people there to tell him that his sister is still alive and in a hospital. They found her. They tell him that she'll be headed there soon. He's in shock and goes most of the day moody and in shock. Amelia notices. She confronts him about it and he tells her what happened.
He has her calling to Germany to find out if it's true. Amelia talks to Teddy on the phone. Teddy confirms it. Owen breaks down again because he can't believe he gave up on her and she was still live. Amelia takes him to Meredith's and Meredith says she'll tell Nathan. Nathan was supposed to go over there for dinner after Meredith decided it was safe to introduce him to the kids. Meredith goes to tell him the news when the explosion happens.