Meredith tries to dismiss a one night stand from her house much like she did Derek many months earlier and like Derek, she's surprised to find the guy at the hospital later that day. Unlike Derek, he's not a doctor but a patient. He has an erection that won't quit, and actual requires medical attention from Meredith, Cristina, and Bailey. For all intents and purposes, it looks to them like Meredith broke the man's penis. And when the cause of the "priaprism" cannot be diagnosed, they have no choice but to call in for a neurological consult from Derek himself. Cristina wakes up to find that Burke has "keyed" her. He not only wants her to have a key to his apartment, he actually would like for her to move in with him. Cristina has issues with this, and she takes Burke to her apartment to show him just how bad of an idea that really is Cristina is the single messiest person in the world.
Alex begins the episode unable to perform with Izzie. A sense of failure hangs over him. Medically, he's assigned to work with Derek on a man with a tumor that's causing him to drink too much water. Dangerously too much water. The man has a sodium imbalance caused by the excess of water, but when Alex gives the wrong order to Nurse Olivia when trying to compensate for that imbalance, he leaves the patient on the verge of death. This is too much for Alex, and in a moment of weakness he and Olivia wind up rekindling their faded relationship and they are in the throes of passion when Izzie finds him. Izzie and George have been assigned to work with Burke and Addison on the quints about to be born. The mother took fertility drugs, to try to have just one daughter and now she has five babies on the way that will all need surgical attention soon after birth. That is disconcerting to Izzie, who wonders why anyone would put her children in such a position voluntarily, especially when the mother had the option to reduce the number of births. But the mother explains it to her quite succinctly: how in the world could she choose, of the five, which ones would be born and which ones wouldn't? The episode ends with all the interns rallying around the mother and her babies as Addison leads her through the complicated birthing nes wouldn't? The episode ends with all the interns rallying around the mother and her babies as Addison leads her through the complicated birthing.