Lea tries to convince Shaun that Steve does not have autism. Shaun wants to consult a pediatric neurologist. Lea says no. She doesn't want to evaluate him every time he smiles. Shaun says that will not help Steve.
Morgan wants Park to get diapers and salsa and skip his workout tomorrow so they can get married to make it easier to adopt Eden. Park wants to be more romantic than that.
A little boy at the hospital can't breathe and the mother says he has severe asthma. He has a third arm under his shirt. The family explains that they believe that's all that is left of his twin.
Park and Jordan see a guy with pain who was at the International Space Station. His wife says he has been having lots of problems since he came back. He might have lost bone mass from being in space. Dom tries to help him set up and his wrist cracks.
Shaun intubates the young patient. SHaun asks Charile if he should get STeve tested. Charlie says he will be misdiagnosed and Shaun will be disappointed.
Glassman tells Hannah she can be discharged. What will she be doing next? She says she's fine, just needs something for the pain. He offers her Tylenol. He tells her she doesn't need anythings tronger. She insists she does. He tells her she's an addict. He says he's trying to help and offers her food.
Park tells Jordan during surgery they do not need her to watch Eden as they are not getting married tomorrow morning. The patient begins coding. After the crisis DOm hnopes he didn't almost kill the patient.
The doctors tell the parents that they have to remove one of the arms. The father wants to remove the big arm and the mother the third arm. Shaun says they will do a test to see which arm is constricting blood flow.
Park and Jordan say they need to implant a defibrillator. The patient's wife says he's a different person since he returned from space. Jordan says that is not a reason to order a brain scan.
Glassman tries to get to know Hannah who doesn't want to talk about where she lives. She says she lives in her car and probably has more friends than he does. She insists she has everything under control. Quitting doesn't work for her. She is not interested in this conversation. Glassman tells her his daughter died of an overdose. He cries, then pays for the food and leaves. He gives her his number in case she needs a meal.
Morgan brings a karaoke machine and sings to Park. He wants to know what she's doing. She says she's proposing.. He says he wanted sincerity and walks away.
Shaun does a Doppler scan. Charlie asks the boy if he's sad. She says she and Dr. Murphy have a condition that makes it hard for them to understand others' feelings. Why is he sad? Tayo says his parents fight about his arm. Shaun recalls his parents fighting and his father saying he doesn't need tests, he needs discipline.
Park and Jordan argue about whether Morgan's proposal was romantic or manipulative. Their patient begins coding. Park realizes the problem has nothing to do with the heart.
During the brain scan the patient imagines he is in o uter space. He doesn't want to leave the MRI machine. HE says he was thinking that the thing he expected to bring him and Ana together is what may break them up. The doctors tell him he has hydrocephalus.
Shaun says it is better to amputate the big arm. The parents argue. Shaun suggests they not do that in front of Tayo as it makes him sad. The parents are shocked and they agree to remove the big arm.
Park says that the hydrocephalus does not explain the persnality change. He says going into space can change perspective. Ana does not want to change their life. She was happy the way things were. Park is sure they can find common ground now. She isn't sure.
Lea is watching Shaun with Steve. Steve is babling. Shaun has a flashback of his father spraying his with water because he wouldn't make eye contact and announces they need to do an evaluation as soon as possible. He wants to do an fMRI. Lea says no. She doesn't want to subject STeve to this. Shaun says he will make an appointment for a study. Lea says no. Shaun gets upset because she gets loud.
Shaun has a meeting about the surgery. Charlie says she and her dad used to watch a car restoration show when she got anxious. Shaun says his dad was not supportive. Charlie says hers was her biggest advocate. Anyway could they strip the big arm to restore the little arm?
Lim tells Glassman to stop being a social worker. Hannah calls.
Tayo's parents are continuing to argue about the procedure. Shaun thinks they should ask Tayo.
Glassman goes to meet Hannah. Someone stole her car. She is crying. Glassman suggests a shelter. She says she needs ar ide to a friend's.
Morgan tells Park he was right. But she was taking this seriously. She tells a story about her great-grandfather. She has his ring. Park takes the ring and kisses her. However he realizes the ring is not what she said and now he won't marry her.
Tayo's parents tell him they fight because they care about him. It breaks his heart that they make him sad. They ask him what he wants to do. He doesn't want to say goodbye to his little brother.
Mason seems to ahve had a stroke.
Glassman takes Hannah to some random place where there are a bunch of people on the street. Glassman doesn't like it but she says her friend got stabbed in a housing-first shelter and goes off. Glassman recalls Maddie banging on the door right before she died. He offers to let Hannah stay with him.
Glassman finds Hannah making breakfast in the morning. She likes to pay her own way. She's going to check out a room for rent. He offers to get her into rehab. She's not interested. He offers for her to stay. She agrees to stay one more night.
Park says they need to remove a piece of the skull to relieve the pressure on the brain. It's a risky surgery but their best shot.
Lea tries to talk to Glassman. She doesn't want Steve to be labeled and seen and different. Glassman thinks she's just scared because of being a new parent.
Meanwhile Shaun does the surgery on Tayo.
Lim says to Glassman she was tough on him yesterday. Glassman knows she was trying to help.
Shaun comes home. Lea asks for a kiss. Shaun kisses her. She says that was quite a thing the other day. He says it upsets him when she raises her voice. She says a child on the spectrum has different needs so she got scared she wouldn't be up to it as a mom. Shaun says that makes no sense because she is a good mother and supportive of him. Lea says they can do the study.
Glassman comes home to loud music. He finds Hannah passed out on the floor. He tries giving her Narcan.
Mason has had his new surgery and now his pupils are reactive. He says he can't go into orbit again but will be okay if he sticks to Earth. Ana is there with him. She says when she thought he was dying she had her own Overview Effect and the world without him would be too cold and empty. Maybe they can start with apuppy before they have kids.
Tayo is in recovery. The parents thanked him for telling them to stop fighting. Tayo awakens and takes his mother's hand.
Glassman watches Hannah awaken. He tells her she OD'd in his house. She says she is sorry. He lectures her about how lucky she is. This can't happen again. She says she'll go. He says that's not what he meant. He's going to give her an oxy prescription. He'd rather she be an addict than she be dead.He will give her pills on a schedule. She says can't you get in trouble? He says let me worry about that.
Park comes home and watches from outside as Morgan dances with the baby.
Shaun recalls his parents fighting about him and his brother giving him ice cream. He watches Lea with the baby at the pediatric neurologist. He asks her if she would like to get some ice cream now.