Season 4 of NCIS: Los Angeles begins where the third season ended with Callen facing the fallout of shooting The Chameleon. He forcefully continues investigating alone and is kidnapped after by hit men. The team tackles many exciting and difficult cases including investigating the death of a former Marine killed in a drone strike in the Middle East. Later, Nell goes undercover in an experimental strategy game developed by the Office of Naval Intelligence when four participants are killed.