Derek and the attendings go out to celebrate when he gets the grant he needs for his clinical trial; Meredith and Alex must fend for themselves during the night shift.
Jane and Maura literally race to find a killer at the Boston Marathon who shoots runners during the event.
The BAU is called to upstate New York to investigate mysterious disappearances. Prentiss receives some disturbing news concerning one of her former Interpol colleagues.
JD finds out that Turk is scared about opening up to him as Turk and Carla make preparations for their wedding. Elliot commits herself to getting back together with her ex-boyfriend.
Gabrielle causes a prison riot while visiting Carlos; Lynette learns that Parker has an imaginary friend; Susan helps Mike search for Zach.
