In 2014, five tourists traveled to the United States to marvel at cacti in the national parks. But when it becomes clear they’re doing more than just looking, U.S. Fish and Wildlife agents begin surveilling the suspects.

In this episode, we examine how there’s a thin line between passion… and obsession. Is there a difference between overzealous collection and callous crime? And does your motivation – whether pure admiration or a paycheck – matter?