When a landlady enters an apartment to collect rent from a tenant, she finds a body in a terrarium instead. The body is slowly being consumed by rats. Meanwhile a new intern named Finn Abernathy is beginning work at the Jeffersonian. Cam is impressed by his credentials and his Southern boy charm. He did a stint in Juvie when he was younger but managed to gain two undergraduate degrees and is working to get his doctorate.
Hodgins collects the rats since they might have eaten evidence and Brennan examines the body, whom she identifies as female in her early 30s. Brennan mentions casually that she's having a girl, which upsets Booth as he wasn't invited to go with her to the doctor. Hodgins finds a snakeskin but no snake, and the team needs to find it because it may have eaten some evidence as well.
Finn examines the body and is shocked when the snake turns up in the victim's abdomen. Cam panics but Finn extracts the snake. Hodgins tries to figure out what landed Finn in Juvie, and Finn admits to some stupid kid stuff: joyriding, robberies, nothing too major. Hodgins doesn't think Finn is telling the entire truth. Cam sees that the victim's teeth contains a lot of food, and Hodgins starts flossing to extract samples of it.Finn notices that the victim could unhinge her jaw like a snake.
Meanwhile Booth and Sweets poke around the victim's apartment. They find out that the apartment belongs to a man named Gerald Sedlack, who is not in the DC area anymore. The apartment is rent-controlled, which means it has changed hands multiple times with the victim being the latest occupant. Sweets notes that the apartment is pretty sparse, which means that the victim might have used it for another purpose. Neighbors claim to have seen the victim, a very attractive young woman, go into the apartment with obese men. Sweets suspects that the victim was a prostitute who catered to a very specific type of "John". Sweets then congratulates Booth on having a daughter, which again upsets Booth. Did everyone know the gender of his baby except him?
Caroline confronts Cam about hiring a felon as an intern, but Cam stands by her decision. Finn's credentials are impeccable and his past shouldn't dictate his future. Finn and Hodgins have to deal with the snake since it has swallowed the victim's distal phalanx and they need to recover it. Cam wants them to kill the snake, and Finn is about to, but Hodgins refuses to do so. Cam gives the pair two hours to get the evidence before the snake digests it, by any means necessary.
Angela has finished her facial reconstruction of the victim, identifying her as Tina Thomas. Booth and Sweets go to talk to Tina's husband, Greg. They skirt around the issue about her having a secret life as a prostitute but Greg says that he approved of Tina's actions and was able to quit his job because she was so good at it. "It" being competitive eating.
Booth tells Brennan that Tina's stage name in competitive eating was "The Python", and she was supposed to have taken part in the Gluttony Games. Booth wants to interview the head of the Competitive Eating Alliance but Brennan can't accompany him because she's made an appointment with a financial planner to create a trust fund for the baby. Booth is again frustrated that Brennan has made a decision about their baby without his input and he wishes Brennan could walk in his shoes for a little while to learn some empathy. Brennan agrees, and will react to situations the way she believes Booth would.
Mitch Clancy, head of the Competitive Eating Alliance, shows Booth some footage of Tina in competition. She was in training for the Gluttony Games before her death and Mitch says that she would have easily won the grand prize. Meanwhile, Caroline has uncovered the reason why Finn was placed in juvie. He assaulted his stepfather and made threats on his life in public. The stepfather then went missing and no one has been able to find his body. Caroline presents this evidence to Cam and asks her to reconsider hiring Finn.
Booth and Brennan attend the Gluttony Games and talks to the winner of the hot dog competition, Ron Patterson. Brennan is fascinated at the inner workings of the human body after ingesting so much food. Ron insists that he didn't kill Tina. He was off training alone on the night of her death.
Hodgins apologizes to Finn for being rude and insistent regarding Finn's past. Finn has figured out that if they cool the snake down, it's physiological processes will slow, which buys them more time to retrieve the evidence from its stomach. Finn points out that snakes may vomit when confronted by a predator, and they scare the snake with a stuffed mongoose. The snake readily throws up the phalanx.
Human skin was discovered in the victim's teeth, and a DNA analysis reveals that the skin belongs to Brian Tobin, head of publicity at Hankfurter Hot Dogs. Brennan swings their car around, imitating what Booth would do when faced with the same situation. Ron's alibi checks out, and Cam asks Angela to quietly look into Finn's past.
Tobin is found yelling at a young woman and trying to shove hot dogs down her throat. Brennan attacks Tobin, which is what Booth would do. Tobin says that he's only helping the woman train. Tobin was coaching Tina that night, and she did bite him because she was growing frustrated over his abusive training methods. Tobin claims that she was slipping in skills and they had fought over money. The last time he saw her, she became upset and threw up, wanting to quit competitive eating.
Angela is reading an article on the incident with Finn and his stepdad and Finn walks in on her. She tries to hide what she was looking at, but Finn quickly changes the subject. He says that they can figure out how heavy the killer was by looking at the damage done by Tina's body being flung into the terrarium, and how much force is required to break the glass.
Finn decides to leave the lab. Brennan notes that Tina's tooth erosion is from vomiting. Tina was throwing up because she was pregnant. After finding out that neighbors reported shouting coming from the Thomas's apartment, Booth goes to talk with Greg again. He admits that he and Tina argued over having kids. They were living comfortably with Tina's competition winnings but if Tina were to have a child, she'd have to quit competitive eating. Greg insists that he just didn't want to start a family yet.
Angela figures out that the killer is very heavy-set, at least 312 pounds. This means that Greg couldn't be the culprit. Brennan takes another close look at the bones to try to figure out who might have killed Tina. Finn returns to the lab, admitting that quitting was pretty cowardly. Brennan point-blank asks him if he murdered his stepdad, and Finn says no, because he knew he'd be caught, probably by Brennan herself.
Finn takes a look at the distal phalanx they extracted from the snake and finds something strange on the bone. Hodgins identifies the round things as lung fluke eggs. The parasite isn't native to the US but is usually found in Japan. Tina hadn't been to Japan lately, but Mitch Clancy had.
Booth talks to Mitch about his parasitical infection and the pills he's been taking to clear his body of it. Booth figures out that Tina wanted to have a baby and to quit competitive eating. Mitch couldn't lose his main means of cash flow so he attacked her. He didn't mean to kill her; he just didn't realize how strong he was when he shoved her across the room.
Cam officially welcomes Finn to the Jeffersonian. Meanwhile, Brennan apologizes to Booth for leaving him out of the baby loop. She and Booth watch a DVD of the ultrasound, happy to share in the first view of their daughter.