Critics from TV Fanatic rated the episode a 4.2 / 5.0 , praising the strong team interaction and the focus on core cast members rather than outside guest stars. While some plot points were deemed predictable, the ideological conflict presented by the DNA group added a layer of complexity often missing from standard procedurals. NCIS: Los Angeles Season 4 Episode 20 Recap: Purity
Review: NCIS: Los Angeles Season 4, Episode 20 – "Purity" "Purity" is a high-stakes, technically intriguing episode of NCIS: Los Angeles that leans heavily into the team’s undercover capabilities. Originally aired on April 9, 2013, the episode centers on a domestic terrorism plot involving cyanide poisoning. NCIS.Los.Angeles.S04E20.HDTV.x264-LOL.[VTV].mp4
: Kensi Blye (Daniela Ruah) and Marty Deeks (Eric Christian Olsen) provide the legwork, with Deeks notably diving into a dumpster to find a critical syringe. Critics from TV Fanatic rated the episode a 4
The investigation begins when a Navy lieutenant is lethally poisoned by cyanide in a communal water jug. The team quickly discovers this was merely a trial run for a much larger attack by a radical protest group known as "Designing a New America" (DNA). Their goal—allocating the defense budget to education—is noble on the surface, but their method is murderous. Standout Moments & Character Dynamics Originally aired on April 9, 2013, the episode
: The episode features interesting trivia about "Prussian blue," a pigment used as an indicator in cyanide tests and a treatment for radiation poisoning.
: G. Callen (Chris O'Donnell) infiltrates the group by staging a public brawl with Sam Hanna (LL Cool J). This leads to a tense sequence where Callen's cover is blown, and he is nearly killed by the very cyanide he's investigating, only saved by a timely counteragent.