Photo Flash: NCIS: LOS ANGELES' Fourth Season Finale, Airing 5/14

On NCIS: LOS ANGELES' fourth season finale, titled "Descent," an explosion in the desert rekindles the search for stolen nuclear weapons and prompts Hetty to shuffle the NCIS: LA partnerships, sending Callen and Kensi overseas and Sam and Deeks teamed up stateside, on May 14 (9:00-10:00 PM, ET/PT) on CBS. Guest stars include Aunjanue Ellis as Michelle Hanna, Christopher Lambert as Marcel Janvier and Timothy V. Murphy as Isaak Sidorov.