Highlights from the Twentieth Episode of Season 4 of NCIS: LA

NCIS: LA searches for a sly culprit in possession of stolen cyanide after a Navy lieutenant is poisoned.

"Purity" Episode 20 of Season 4

Pictured: LL COOL J (Special Agent Sam Hanna) and Chris O'Donnell (Special Agent G. Callen). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Cliff Lipson/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.
Uniformity in

Uniformity in "Purity" Episode 20 of Season 4

Pictured: LL COOL J (Special Agent Sam Hanna). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Cliff Lipson/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.
Photo Snapping in

Photo Snapping in "Purity" Episode 20 of Season 4

Pictured: LL COOL J (Special Agent Sam Hanna). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Cliff Lipson/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.
Protest in

Protest in "Purity" Episode 20 of Season 4

Pictured: LL COOL J (Special Agent Sam Hanna) and Chris O'Donnell (Special Agent G. Callen). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Cliff Lipson/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.
Held Back in

Held Back in "Purity" Episode 20 of Season 4

Pictured: Chris O'Donnell (Special Agent G. Callen). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Cliff Lipson/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.
Dumpster Diving in

Dumpster Diving in "Purity" Episode 20 of Season 4

Pictured: Daniela Ruah (Special Agent Kensi Blye) and Eric Christian Olsen (LAPD Liaison Marty Deeks). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Monty Brinton/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.
Table Service in

Table Service in "Purity" Episode 20 of Season 4

Pictured (L-R): Eric Christian Olsen (LAPD Liaison Marty Deeks), Daniela Ruah (Special Agent Kensi Blye) and Mark Espinoza (Detective Lopez). 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, on NCIS: LOS ANGELES, Tuesday, April 9 (9:00-10:01 PM, ET/PT) on the CBS Television Network. Photo: Monty Brinton/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.