Sam's sister, Corinne (guest star Anika Noni Rose), is a near-catatonic state after being drugged up by various sedatives prescribed by prison doctors. Sheldon takes her off all meds in order to bring her back into a coherent state. It's the only way he can properly analyze her. This could be risky since Sam remembers her being somewhat wild as a child.
Jake warns Addison that it's not her job to watch after Sam even though he's hurting. It's also not her job to have sex with her ex, but Addy does so anyway. Jake says, "Okay, I should have seen that coming." Ouch. As for Sam, he's keeping a close eye on Corrine who seems to be coming out of her haze. Her recollection of a memory from their childhood is enough to bring her big brother to tears.
Cooper and Pete treat a newborn baby, Eli, who was brought into the hospital by his 19-year-old sister, Denise. That's because the baby's mother, Melissa, is a drug addict who has been MIA for over a week. She had locked herself in a hotel room to get clean by going cold turkey. She was a horrible mother to Denise, but wants a second chance with Eli.
Denise believes her mom is going to hurt Eli just like she hurt her. Melissa swears she's clean. The two of them get into a huge argument that ends abruptly when Eli starts to crash. Addison is able to save the baby, but it'll be a long road to recovery. Melissa tries to convince Cooper that she'll be there for her son. He's swayed enough to convince Denise to help her mom fight the good fight together as a family.
Things are heating up between Violet and hot Scott. Needless to say, Pete's not thrilled to catch them making out in the hospital hallways. Violet says her relationship is just about sex. It's not going anywhere. Cooper suggests she tell Pete that. So she does. Violet says he shouldn't care, but seems pleasantly surprised when he admits that he does.
Erica has started her chemotherapy. Cooper and Charlotte are reluctantly respecting her wish to keep Mason in the dark about the treatments. Amelia is desperately looking for a miracle surgery to treat Erica's tumor. A trip to New Zealand has promise, but the frightened patient puts the kibosh on any international flight plans. As for Mason, he so desperate to see his mom that he runs away from home.
Charlotte frantically searches the streets as soon as she realizes Mason is gone. Thankfully, she finds him safe and sound. The boy is scared. He thinks his mom is dead. Charlotte holds him tight and brings to the hospital where Erica assures him that she's going to be just fine. Thanks to Amelia, there may be a sliver of truth to that statement. She thinks big brother Derek can help. Erica didn't want to go to New Zealand, but she seems up for a trip to Seattle.