Pirillo reconsiders how diplomacy worked, not only within but also outside of formal state channels, through underground networks of individuals who were able to move across confessional and linguistic borders, often adapting their own identities to the changing political conditions they encountered. Through a trove of diplomatic and mercantile letters, inquisitorial records, literary texts, marginalia, and visual material, recovers the agency of religious refugees in international affairs, revealing their profound impact on the emergence of early modern diplomatic culture and practice.