Dexter Season 5 Episode 7 (Dexter s05e07) with title “Circle Us” aired on Sunday, November 7th 2010 at 09:00 pm via Showtime Network.
Here is summary for Dexter Season 5 Episode 7 :

While helping Lumen, Dexter finds himself on a collision course with Debra and the rest of Homicide when he is called to investigate a horrifying crime scene; the Santa Muerte case leads to a violent standoff between Debra and the killers.