Ecologist Nick Haddad was sitting in his new office at North Carolina State University when the phone rang. On the other end of the line was... The U.S. Army. The Army folks told him, “Look, there’s this endangered butterfly on our base at Fort Bragg, and it’s the only place in the world that it exists. But it’s about to go extinct. And we need your help to save it.” Nick had never even heard of the butterfly. In fact, he barely knew much about butterflies in general. Nonetheless, he said yes to Uncle Sam. “How hard could it be?” he wondered. Turns out, pretty hard. He'd have to trick beavers, dodge bombs, and rethink the fundamental nature of life and death in order to rescue this butterfly before it disappeared forever. **CORRECTION: An earlier version of this story incorrectly stated that the Army moved a beaver; in truth, they killed it.  We also overstated the current tally of St Francis Satyrs off range; they are around 200, not 800. The audio has been adjusted to reflect these changes.**This episode was reported by Latif Nasser, and produced by Rachael Cusick. Original music by Jeremy Bloom. Mixing by Arianne Wack. Special thanks to: Snooki Puli, Cita Escalano, Jeffrey Glassberg, Margot Williams, Mark Romyn, Elizabeth Long, Laura Verhegge, the Public Affairs and Endangered Species Branches at Fort Bragg. Want to learn more? you can ...... read Nick Haddad’s book The Last Butterflies: A Scientist’s Quest to Save a Rare and Vanishing Creature... take a peek at Thomas Kral’s original 1989 paper about the Saint Francis Satyr... visit Fort Bragg's webpage about the Saint Francis Satyr  Support Radiolab by becoming a member today at Radiolab.org/donate.