Dangerous Assignment - Recover Stolen Dynamite

Agent Steve Mitchell walks into the Commissioner's office and says "Good morning, Commissioner, Ruth left a note on my desk that said you wanted to see me. Incidentally where is she?" Commissioner says "Down at the Red Cross donating some blood. I gave her the day off". Steve says "I've got a date for the same thing". Commissioner says "Every American should donate blood to the Red Cross, but right now, take a look at this". Steve says "A piece of string?" Commissioner says "Describe it to me as accurately as you can".  Steve says "Okay, it's about a foot long". Commissioner says "Eleven inches to be exact". Steve says "Okay, eleven inches. It's got four knots, and they're unevenly spaced. That's about all I can see. So, you're a string saver, Commissioner. Is that what you called me in here to tell me?" Commissioner says "Not exactly. In the first place, I have a hunch that's about the most important piece of string in the world right now. In the second place, it's not mine. It belongs to Jim Slater". Steve says "Oh, is Jim back? That's good". The Commissioner says "Jim's dead, Steve. He was murdered in Panama the night before last. He was one of your best friends, Steve, that's why I figured you'd want to take over his assignment". Steve says "Yeah, I do, but I never knew what Jim was working on. He just dropped out of sight about a month ago". Commissioner says "Very few people did know about his assignment, Steve. I sent him to Panama a month ago". Steve says "Panama? What's going on down there?" Commissioner says "Plenty, I'm afraid.  Jim Slater was down there investigating a series of thefts that have been going on for the last six months. Civilian construction camps and army engineer stations have been systematically burglarized". Steve says "Look, isn't that a matter for the national police in Panama?" Commissioner says "What's been stolen makes it strictly our business". Steve says "Oh, well, what exactly has been stolen?" Commissioner says "Dynamite, and  It looks like he was on the trail of something, Steve".