Arizona tries to reconcile with Callie, who has big news to share; Teddy faces an important decision; the residents receive new interns; the Chief makes an announcement.

Richard performs a monumental surgery in his career; Derek and Lexie attempt to work miracles for a patient with an inoperable tumor

A lion breaks loose in Seattle, leaving a couple's lives and relationship at risk; Lexie overhears Mark's discussion about moving in with Julia; Teddy begins to take steps towards coming to terms with Henry's death; Callie grills Arizona on her past lovers; and Alex requests to be taken off Morgan's preemie case when she becomes too dependent on him. Meanwhile, Meredith tries to be a support for Cristina as the tension between her and Owen hits a boiling point.

The new batch of interns find themselves involved in all the drama at Seattle Grace: Meredith asks Heather to go above and beyond to help fix Derek's hand; Cristina starts a healthy competition between Stephanie and Leah, which inadvertently leads to a medical emergency for Cristina's patient; Alex sees Jo in a new light as they work to save a baby's life, and April teaches Shane a valuable lesson during "lumps and bumps" duty.

A gas tanker explodes on a Seattle highway, causing multiple injuries, including paramedic Matthew. Meredith and Jo help a frantic mother whose child is suffering from a mysterious illness. Owen bonds with a young boy whose parents are in critical condition. Meanwhile true colors are revealed when Alex is forced to work with Jo's boyfriend on an ailing patient.

The hospital doctors become fascinated with Dr. Herman’s case when Amelia gives a lecture detailing the intricacies of the surgery. Arizona and Herman continue to bond over the amount of cases they are trying to complete before the big surgery. Meanwhile, Bailey brings them a case of a pregnant woman who is close to her heart.