'NCIS: LA's Eric Christian Olsen Previews Hetty's Heartbreak in Episode 250

Kate Hahn
Preview Ron Jaffe/CBS

Sunday's milestone episode is a real inside job. It's written by NCIS: Los Angeles actor Eric Christian Olsen (above) — aka scruffy, quick-witted detective Marty Deeks — who went big on his first script (cowritten with Babar Peerzada) for the drama: The team is targeted by an embittered black-ops agent originally recruited by top boss Hetty Lange (Linda Hunt).

After sending the script for No. 250 to Hunt, Olsen sat by the phone nervously waiting for her response. Upon hearing she loved it, he cried. The action- and emotion-packed hour — which contains 104 scenes vs. the usual 40 to 60 — asks a lot of the actress.

"Hetty's heart is breaking," he says. Her former protégé, South African Ahkos Laos (Carl Beukes), believes "the only way to stop the cycle of violence is to take the lives of the people creating it."  

The unit's members — notably Callen (Chris O'Donnell), who was also trained by Hetty — realize they could have turned out like Ahkos if they had worked solo.

Who Should Be the Next Hetty on 'NCIS: LA' — Callen or Nell? (POLL)

Who Should Be the Next Hetty on 'NCIS: LA' — Callen or Nell? (POLL)

Hetty's plans for her replacement may have changed after 'Kill Beale Vol. 1.'

"Our characters have to do incredibly violent things, [but the show] doesn't really talk about the emotional repercussions," says Olsen, who for research read the nonfiction book On Killing: The Psychological Cost of Learning to Kill in War and Society.

Next week, look for another special episode. December 8's "Answers" addresses viewers' long-swirling questions and theories. Says Olsen: "It's like a holiday gift to the fans."

(Bill Inoshita/CBS)

NCIS: Los Angeles, Sundays, 9/8c, CBS