A letter concerning a colleague...

It had been about a week since Nat had returned home after helping excavate the ruins of a Cambodian temple. He and his team had made several interesting finds, but it was nothing groundbreaking. It seemed to him like he was back to the comparatively dull life he led between expeditions. The typical teaching classes at a university and occasionally giving the odd speech at a museum. This all changed, however, when he received a rather worrying letter from the wife of one of his colleagues...

Well wishes, Professor Jones.
I write to you with very unsettling news about Adam Warren. As you likely know, he and I moved to Brazil about a year ago after he was hired to teach at the University of Sao Paolo. A few weeks ago, he said he was going to go into the jungle to "look into something about some tourists..." I'm paraphrasing, but that was the gist of it, anyway. He told me to write to you if his group was not back within a week, and to ask you to, for lack of a better term, rescue him. I hope he's safe...
-Mariah Warren

Nat frantically scanned the letter again, almost certain he'd misread something. He didn't. Adam Warren had gone on a dangerous journey into the Amazon Rainforest and asked his wife to contact, not a search and rescue team, not even the police, but his friend Nat Jones, should he go missing. Sure, Nat was a very smart man and over the years had performed a few feats of heroism that not even he had expected, but this seemed like an incredibly reckless decision on Adam's part. "Whelp, guess I'm going on another expedition sooner than I thought..." Nat sighed to himself as went to pack his supplies.