The episode's central medical emergency involves a catastrophic tunnel collapse that crushes 20 cars, resulting in high casualties.
: Meredith, Maggie, Amelia, and April are dispatched to the site to assist victims. [S11E23] Time Stops
While the medical emergency drives the plot, the underlying tension remains focused on the loss of Derek. resulting in high casualties. : Meredith
: The chaos introduces a new group of surgical interns, including Andrew DeLuca , who initially appears to be an attending surgeon after he jumps in to help a pregnant victim at the crash site. Emotional Aftermath & Confrontations including Andrew DeLuca