Joel Grimwood was almost certainly going to die. The pump that kept his failing heart going had become infected, and surgery after surgery had scraped away parts of his chest. Drugs didn’t work because the bacteria were in a slime, impenetrable to antibiotics. What saved his life was a little-known treatment called phage therapy. Popular in the former Soviet Union, they’ve fallen out of favor in the West. The viruses are the natural predator of bacteria, and a small number of scientists are trying to turn them against the threat.