The brokers who forge networks have exclusive access to diverse and innovative information. Hence, many histories of the Republic of Letters (1500–1800) stress the importance of brokers for the circulation and development of new ideas. But most such studies fail to note that network brokerage in the Republic of Letters was a dynamic, continually evolving process. Early modern brokers, like the Florentine librarian Antonio Magliabechi (1633–1714), could not have maintained their positions of power in densely connected networks without the ability to safeguard confidences and secrets. Qualitative analysis of archival sources, combined with the quantitative methods of network analysis, uncovers the circumstances in which Magliabechi constructed his network, providing a glimpse into his struggles to make it secure and to solidify it with valuable bridge relations.