Meredith and Derek get one last shot at success in their clinical trial; the surgeons work together to free a boy from a block of cement; Izzie helps Alex care for Rebecca; Lexie uncovers critical information about George's status as an intern.
The team is called away to the Apalachian Trail in Virginia, after a state trooper, discovers a bag of dismembered body parts. Emily Prentiss returns to the BAU.
The team reopens the 1970 murder case of a 20-year-old musician named Billy, who kept his involvement in Philadelphia's music scene a secret from his strict preacher father.
When Violet files for joint custody of Lucas, Pete fights back, forcing friends and co-workers to choose sides.