12. The Abyss

CGIS Agent Abigail Borin busts Julio on human smuggling, then finds two murdered grad students aboard the research vessel Acadiana; diver/oceanographer Mark Post and ecologists/biologist Cindy Rutberg, and a third crew-member missing, biologist Anna Huntley, daughter of Navy Admiral Adam Huntley. After analyzing paint transfer, the high-end boat thief Clive Roberts is apprehended, but he has an alibi for the murders. Video footage is found that shows Anna holding a Beretta during the attack. Brody suggests re-checking Anna's shipmate bios supplied by her advisor, Dr. Sandra Jones of the Gulf Coast Oceanographic Institute.

Sandra suggests there may have been a love triangle. Also, Anna is $90,000 in debt. Sebastian narrows the search area where silver pesos from the mid-1700s Spanish wreck El Cazador are found on the ocean floor, providing another motive. Patton Plame discovers that Steve Merris is selling them for bitcoin on the dark web. Steve claims Anna is his competition, and provides her screen name. The team sets up a buy, but instead catch Professor Jones, not Anna. Pride gives Anna's father the bad news after recovering her body. Meanwhile, LaSalle finds his missing older brother Cade in jail and still struggling with bipolar disorder.