Watch the first trailer for Oxygen's latest true-crime show, 'An Unexpected Killer' (Exclusive)

Oxygen's latest true-crime series will leave its viewers on the edge of their seats.

"An Unexpected Killer" takes a closer look at a series of homicide investigations that appear to be inching closer to an answer before investigators are thrown for a loop by uncovering something unanticipated in their investigations.

Premiering on Thursday, December 5 at 8PM EST, the first episode of "An Unexpected Killer" is called "Modern Family Murder" and examines the brutal 1984 murders of Robert and Kathryn Swartz. Investigators will uncover dark secrets related to the couple "leading them to a suspect no one saw coming."

Get an exclusive first-look at Oxygen's "An Unexpected Killer" in the AOL exclusive trailer at the top of the page, and tune into the premiere episode on Thursday, December 5 at 8PM EST.