Abstract: Research on social networks has begun to take advantage of data that reveal fine-grained communications over time and their role in coordination, decision-making, and information sharing. These studies, however, have focused primarily on social communication as a phenomenon that is endogenous to the network; they have not generally analyzed how changes to the communication structure are associated with external events. How social networks structurally respond to external events, and how structural changes predict shifts in the networks communicative functioning, are questions that have remained largely unanswered. I will present a study on how external events are associated with a network’s change in structure and communication content. Analyzing all the millions of instant messages of the decision-makers in a large hedge fund and their network of hundreds of outside contacts, we investigate the relationship between stock price shocks and changes in the structure and content of the firms decision-making network. We find that when price shocks occur, the communication network tends not to display structural changes associated adaptiveness. Rather, the network turtles up -- exhibiting higher clustering, more strong tie interaction, and intensified internal communication. Further, we find that changes in network structure uniquely predict shifts in message content, including the emotional and cognitive engagement of decision-makers in the firm.