WHEN A YOUNG MILITARY WIFE VANISHES, NCIS AGENTS DISCOVER A SECRET AFFAIR AT THE MARINE COMBAT BASE IN TWENTYNINE PALMS, CALIF.

"48 Hours: NCIS: The Marine's Wife"

Tuesday, June 12, 10:00 PM, ET/PT

Erin Corwin was just 19 when she kissed her husband goodbye and said she was heading to Joshua Tree National Park to scout out hiking trails. The morning of June 28, 2014 was the last time her husband, Corporal Jon Corwin, saw her alive.

The investigation into what happened to Erin Corwin after she left home would expose a secret affair between two neighbors in the Marine Combat Base in Twentynine Palms, Calif. It would also take months of painstaking investigative work to get answers - and closure - for Corwin's family members.

"This isn't a case. This is not a number - this is a human being," says NCIS Special Agent Clifton Randolph in 48 HOURS: NCIS: "The Marine's Wife," to be broadcast Tuesday, June 12 (10:00 PM, ET/PT) on the CBS Television Network. "You can't forget that this person has a family, has a husband, has a mother. They wanted to know where Erin was. And you can't forget it."

48 HOURS: NCIS is a six-part series from the award-winning team behind 48 HOURS that takes viewers inside the difficult cases faced by NCIS agents, who investigate murders, track killers and use the latest technology to solve cases that once seemed unsolvable. Rocky Carroll, star of CBS' drama series NCIS, is again the narrator in the second season of the series.

Initially, investigators turned to Erin Corwin's husband for answers. There were questions about why he waited 24 hours to report her missing. However, Jon Corwin passed a polygraph test, and digital evidence led them to believe he had been on base the day his wife went missing. He was not considered a suspect.

Meanwhile, base commanders flooded Joshua Tree National Park with troops to help look for her in temperatures that reached as high as 115 degrees.

"It's a lot to take in, especially from probably your least adventurous child - a child that you would probably never expect something like that to happen to," says Lore Havelin, Corwin's mother.

Investigators learned Erin Corwin wasn't going to scout trails that day, but rather to meet a married neighbor, Corporal Chris Lee. They allegedly had fallen in love after Erin had a miscarriage. Corwin had befriended Lee's family, even becoming a babysitter for Lee's daughter. Her car was found abandoned far from the entrance of Joshua Tree National Park. She was nowhere to be found.

An NCIS specialist would conduct a digital forensic analysis of Erin's social media accounts and would soon learn that Erin had told a friend in Tennessee about the affair, and Erin had confided to her that she was now pregnant and the father was Christopher Lee.

Two months after Erin Corwin disappeared, her body was found dumped in one of the more than 1,000 abandoned mines in the unforgiving desert - a discovery, Erin's mother said, that "was like finding a needle in a thousand haystacks."

How did she get there, and who would kill Corwin? And could NCIS agents track down the killer?

"I think agents become so attached to these cases because it's such a huge investment," says NCIS Director Andrew Traver. "It's not a 9-to-5 job. It takes so much focus, so much energy to stay on some of these cases, to follow them through the end."

48 HOURS: "The Marine's Wife" is produced by Paul LaRosa. Laura Ramirez is the field producer. Michael Baluzy, David Spungen, Karen Brennan and Gregory Kaplan are the editors. Marlon Disla and Phil Tangel are the series' producer-editors. Jonathan Leach is the coordinating producer. Asena Basak is the development producer. Rob Klug is the director. Anthony Batson is the executive producer. Susan Zirinsky is the senior executive producer.

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