The episode begins, and Meredith is convincing Derek she's excited about the house -- and they see a wild lion roaming the streets of Seattle while they're on their way into work. It's been a week since Owen and Christina talked. Teddy is in a support group for widows, and she's laughing while another widow tells a story about how her husband died of congestive heart failure. Christina doesn't really believe Meredith's story about the lion. Owen isn't paying much attention to her story, either. Meredith says Animal Control shot it with one dart. Derek can't convince Sloan to pay much attention to the lion story, either. Sloan is considering asking Julia to move in with him.
Lexie is in the back of the elevator and overhears this. Webber and Avery wait for the ambulance to bring in patients from a lion mauling. Avery mocks Webber for trying to get in on it rather than doing a gall bladder operation. A 32-year-old man who was mauled by the lion comes in, and he's worried his girlfriend was eaten by it. A woman in, also badly injured by the lion, asking about Kirby. Bailey tells her the man is fine, but the injured woman corrects Bailey, saying that Paul is the boyfriend -- Kirby is her lion. Teddy tells Arizona and Christina about her bad grief group experience. A nurse comes to say goodbye to them, and she asks whether it's OK for her to give Arizona a hug. She holds the hug for a long time.
Alex is taking care of Morgan's baby, Tommy, and he sneaks away to tell Arizona he needs to get off the case because Morgan is "into" him. Arizona lets him off her service. Bailey explains to Owen and Meredith about the woman keeping the lion as a pet. She wants to save the woman's life, just so she can tell her she's crazy. Owen asks Meredith to tell Christina how sorry he is and that "it was just sex" and he'd take it back if he could. Meredith gets upset and tells Owen she wants to pretend their conversation never happened. Callie tells Sloan about the nurse, Colleen, and the lingering hug and realizes that she and Arizona must have had a thing. She's also wondering if Arizona has had other flings with other nurses. Christina and Teddy start working on a stem-cell experiment to grow new hearts. Alex walks in and announces that he's on Teddy's service, and they both get paged to the E.R., leaving Christina alone.
Derek walks Lexie through an aneurysm clipping procedure. She thinks Derek is worried about her doing it, but he says she has to learn. She asks Derek if he's going to suggest to Mark that he move in with Julia, and after she awkwardly stammers for a bit, she and Derek both agree they "don't talk about stuff like this." April is treating Morgan's baby, and Morgan wants Alex to be paged. April tells a nurse to page Arizona. Teddy and Alex are treating an elderly man and Alex gets repeated pages. The man and his wife reveal that what might have triggered the heart pain was the excitement over having seen the lion. Callie asks Arizona about whether she and Colleen were "a thing," and Arizona says they were "a little bit of a thing a very long time ago." Callie asks if there were other exes in the hospital. Arizona doesn't want to have the conversation. Callie asks for "a number" and Arizona says, "1 or 2." Bailey operates on the injured woman and talks about how she should have gotten a dog instead of a lion as a pet.
Owen and Meredith are awkwardly quiet. Bailey asks if she's offended anyone without realizing it, and she asks Owen if he has any exotic pets. "Christina doesn't believe in pets," he says. Meredth quickly shoots back, "Christina doesn't believe in a lot of things." Alex and Teddy tell the wife of the elderly man that he had another heart attack during his surgery. He apologizes to his wife for messing up their Alaskan cruise. They were going to celebrate 50 years together. Derek tries to prep Lexie for surgery but she's still distracted by the Sloan situation. Derek tells her he needs his resident to focus. Christina works in the lab while Alex and Avery come in for lunch. Alex talks about how Morgan won't stop paging him. Lexie shows up and says she understands the woman keeping a lion as a pet.
Christina asks them to leave. Arizona and April tell Morgan about her baby's condition, but she's focused on where Alex has gone. Arizona opens up the possibility of allowing natural death for her child. Arizona tells her she should consider what kind of life he'll live. Alex comes around and sees Morgan crying. She tells him about Arizona's comments and he walks away. Sloan, Callie, Avery and Webber are operating on the man who was mauled by the lion and talking about Arizona's "1 or 2" exes. Webber clears his throat and reminds Callie that when patients say they have "1 or 2" drinks each week, they round that number up because they're likely having many more. Just then, Avery finds a lion tooth and pulls it out of the man's body. Webber wants a nurse to keep it safe.
The elderly man's wife talks with Teddy in the waiting room and asks Teddy to do whatever she can to save her husband. Teddy assures her she's "very good" at her job. Derek and Lexie operate on their patient and Derek takes over. Lexie steps aside. Derek then says he's not going to tell Sloan what to do. He says Sloan might change his mind to move in with Julia if he thinks there's still a chance with Lexie. But he tells Lexie to make sure she really wants to be with him, not that she just wants him because he's with someone else. Alex and Teddy are in surgery when a nurse reads Alex a string of texts from Morgan. Teddy tells Alex he's doing the right thing by ignoring her. Alex asks the nurse to turn his pager off. Hunt tracks down Meredith and she again gets upset with him.
She tells him that Christina didn't want her to know about Hunt's affair, and now she does. Teddy gets through a particularly tricky part of the surgery on her patient, and Alex is impressed she did it. Sloan warns Arizona that Callie is on a mission to learn more about Arizona's exes. Callie asks Arizona for names. Arizona points out a few women in the cafeteria, and then lists a few more names. The man who was mauled by the lion talks about how he was trying to live up to the man he hoped he could be by facing his girlfriend's lion. Webber tells the man he's a hero for jumping in front of the lion when its real target was the man's girlfriend. Teddy and Alex are on their way to tell the elderly woman that her husband is OK when Morgan stops Alex. Morgan wants to know what Alex thinks. He gives her his medical opinion, but she doesn't want that. He gets harsh with her, telling her she has to deal with her own situation without involving him. Meredith finds Christina in the lab and Christina explains the process of making new hearts from scratch.
Teddy finds the elderly woman in the waiting room unconscious. Alex sees Morgan sitting next to her baby through a window. Arizona tells Alex they're doing the surgery but Morgan doesn't want Alex involved. Arizona says Tommy is going need "a really tough mom," and if hating Alex helps make her tough that's alright. Paul, the lion victim, gets moved in next to his girlfriend Naomi and she blames him for the fact that her lion is now gone. Sloan finds Callie looking at a board of doctors in dermatology, saying she's trying to figure out how many other people Arizona's likely hooked up with. Sloan reminds Callie that Arizona wakes up every morning and sees Sloan holding the baby that he and Callie made together. Callie realizes that "can't be easy" for Arizona and Sloan insists it must be killing Arizona to know that Callie was "with the golden boy of this hospital." Teddy's patient thanks her for the successful surgery, and that he has the heart of a 50-year-old. He asks for his wife, and Teddy tells him that she went to find his wife in the waiting room and she was unconscious.
She was pronounced dead just minutes earlier. He cries and holds Teddy's hand. Bailey gives Owen a little pep talk, telling him that while he did a terrible thing, he's not a terrible person. Teddy cries as she looks at herself in the mirror and declares, "I am a widow" repeatedly. Lexie and Sloan end up in the same elevator that night. They nearly walk together to the parking lot, but Lexie decides to stay late to do more work. Webber shows Avery his massive collection of the items that have been removed from patients. He's stored them all in jars. He tells Avery they sometimes get geniuses on their surgical tables and they sometimes get idiots.
"I, for one, am partial to the idiots," Webber says as he drops the lion's tooth into a new jar. "You don't get a lion's tooth from a genius." Callie gets home that night and proceeds to use her "fight" with Arizona as a primer for sex. Meredith gets home and tells Derek that if he ever cheats on her, she'll kill him. She makes him promise he'll never cheat on her, and he does. He asks if she wants to talk about it and she says no. Owen gets home and he and Christina sit in silence at their dinner table. Suddenly, she splashes her bowl of cereal in his face. The episode ends at this point.