Scott Michael Morgan

Dexter continues his manhunt for the Brain Surgeon. Dr. Vogel tries to prove to Dexter that he's perfect as a psychopath. Debra's PTSD kicks in and she makes a desperate plea to confess to LaGuerta's murder.

Miami Metro continues their hunt for the Brain Surgeon while Dr. Vogel enlists Dexter to do her bidding based on her own personal experience with her previous patients. Debra continues to track down her P.I. case and has to take matters into her own hands.

Frankie urges Sue to stand up for herself at school.

It's Christmastime and both Marshall and Robin are feeling homesick in New York, and Ted's immature younger sister Heather arrives in the city. Ted has been trying to keep Heather and Barney apart because he fears they will sleep together. Barney and Heather prove Ted wrong and Ted is forced to admit that his sister has grown up.

In the midst of flu season, a sick Leslie and Andy struggle to book performers for the Unity Concert.

Susan eases her overwhelming feelings of guilt by making some dangerous choices, and Gaby plans a sexy surprise to help Carlos gain his sexual mojo back.