Clostridium difficile infection is the most common cause of antibiotic-associated diarrhea in developed countries. Researchers have discovered how the C. diff toxin B recognizes the human Frizzled protein, the receptor it uses to invade intestinal cells and lead to deadly gastrointestinal infections. The findings could pave the way for new C. diff antitoxins and also show potential for the development of novel anti-cancer drugs.