In "Grunt", Roach tackles the science behind some of a soldier's most challenging adversaries?panic, exhaustion, heat, noise?and introduces us to the scientists who seek to conquer them. She dodges hostile fire with the USMC Paintball Team as part of a study on hearing loss and survivability in combat. She visits the fashion design studio of U.S. Army Natick Labs and learns why a zipper is a problem for a sniper. She visits a repurposed movie studio where amputee actors help prepare Marine Corps medics for the shock and gore of combat wounds. In east Africa, we learn how diarrhea can be a threat to national security. Roach samples caffeinated meat, sniffs an archival sample of a World War II stink bomb, and stays up all night with the crew tending the missiles on a nuclear submarine. She answers questions not found in any other book on the military: Why is DARPA interested in ducks? How is a wedding gown like a bomb suit? Why are shrimp more dangerous to sailors than sharks?