Glimpse of secretive 86-day Infantry Officers Course

A television crew on assignment for 60 Minutes followed some young Marines to the Mojave Desert recently. The crew, which included CBS News' Mary Walsh and David Martin, were there to see the final hurdle in the rigorous 86-day Infantry Officer Course, the test that Marines must take to become platoon commanders.

The TV crew was there to report on the test, but the grueling two-day hike in 110 degree heat was a test on another level for the reporters.

"Basically, it was to prove to the Marines that we were 'all in' on this story," says correspondent David Martin. "They weren't going to just give up their secrets for a drive-by story where somebody came and shot a few frames."

So, to get past that skepticism, Martin and producer Mary Walsh had to literally put sweat equity into the story.

"It was so hot," says Walsh. "And the mountain itself is just all stone....I actually fell almost immediately and I had a lump on the side of my head. I really thunked myself."

"Basically, it was to prove to the Marines that we were 'all in' on this story. They weren't going to just give up their secrets for a drive-by story where somebody came and shot a few frames."

And that was just the beginning of the trip's mishaps for the 60 Minutes team. In addition to sliding rocks, attacking bees, nighttime scorpions, and the occasional rattlesnake, the team's greatest challenge was the desert heat. The heat was so intense, the soles of Martin's boots came unglued, flopping off. Walsh became so depleted at one point, she experienced a mountaintop "meltdown."

"Somehow I just ran outta gas," Walsh tells 60 Minutes Overtime's Ann Silvio. "I just was down and done."

And that was Day 1 for the 60 Minutes team. For the Marines taking the arduous test, it was Day 70. Watch them both tough it out in this week's 60 Minutes Overtime interview in the video player above.

Overtime segment produced by Ann Silvio and Sarah Shafer