NCIS: Los Angeles backdrop
NCIS: Los Angeles S4E20 — Purity
7.6

Purity

7.6/10 · 352 votesApr 9, 201344 min

Ranked #18 of 24 in Season 4•−0.1 vs season avg

Discussion

When cyanide in a communal water jug lethally poisons a lieutenant and leaves a Navy pilot in serious condition, the NCIS: LA team investigates whether this is an isolated incident or an early test for large-scale water contamination.

Season 4 Episodes24

Cast7

Chris O'Donnell

Chris O'Donnell

G. Callen

Daniela Ruah

Daniela Ruah

Kensi Blye

Eric Christian Olsen

Eric Christian Olsen

Marty Deeks

Barrett Foa

Barrett Foa

Eric Beale

Renée Felice Smith

Renée Felice Smith

Nell Jones

LL Cool J

LL Cool J

Sam Hanna

Linda Hunt

Linda Hunt

Henrietta "Hetty" Lange

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Episode Summary

"Purity" is episode 20 of NCIS: Los Angeles season 4. It scored 7.6/10 from 352 votes, ranking #18 of 24 episodes this season (season average 7.7). It aired on April 9, 2013.