What better way to celebrate a milestone than allowing a star to help write it?

For the 250th episode of NCIS: Los Angeles airing this Sunday, Eric Christian Olsen, who stars as Marty Deeks, pulled double duty in the writers’ room by co-penning “Mother,” the milestone episode that revolves around Hetty (Linda Hunt). Here’s the official logline for the script also written by Babar Peerzada: “Akhos Laos (Carl Beukes), a former black ops agent originally recruited and trained by Hetty Lange, has returned to seek revenge for the life she introduced him to.”

“In today’s splintered media landscape to be a part of a show that is celebrating its 250th episode is absolutely unbelievable,” Olsen tells EW. “To be given the opportunity to write the episode is an incredible privilege. The whole thing is surreal. I couldn’t be more humble, excited, and grateful.”

In this exclusive first look above, Kensi (Daniela Ruah) discovers a clue that’s anything but a cup o’ joe, while Callen (Chris O’Donnell) and Sam (LL Cool J) open up one helluva Pandora’s box. Gotta hand it to Olsen — that’s quite a twist!

NCIS: Los Angeles airs this Sunday at 9:30 p.m. ET on CBS.

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