Some dogs were born to be more than just man's best friend. The dogs of US Customs and Border Protection work day and night to stop the flow of illegal contraband across the border. Puppies with promise begin their careers at the El Paso training center, where they're matched up with their human partners. Together the pairs learn tools for the job, and dogs hone their unique canine skills. While we watch the patrol team's progress in training, we witness a variety of stories as they happen in the field with veteran teams. Expert canines sniff out drugs in trucks, trains and semis, keeping dangerous substances off the streets. Other pups work with their partners to patrol the long stretch of desert on search and rescue missions. In every high-stakes situation, the canines are key to success.