The show is leading everyone to believe that Doc Vogel is the brain surgeon. Showing her looking at a brain specimen as if it were a trophy straight after Zach's body was found by Dexter implies that she isn't actually the killer.
The real killer is either Cassie's boyfriend Oliver OR (and this is a long shot ) Joey Quinn.
The real killer is either Cassie's boyfriend Oliver OR (and this is a long shot ) Joey Quinn.