This article examines the role that native engineers trained in a foreign country play in international technology transfer, a topic in which the human factor has often been assumed as 'tacit knowledge' by historians of technology. The discussion explores the case of Basque engineers who graduated from the University of Liège in Belgium between 1850 and 1914. I first show that the high number of these graduates was, to a large extent, the result of a specific educational strategy, and will analyze the underlying social and entrepreneurial reasons for this. Next, I follow the actual interactions that took place between foreign suppliers and client companies, revealing a complex process in which the engineer (from hereon linking agent) served as a bridge between two places. Drawing on specific historical episodes of the Basque iron and steel industry, I examine the roles played by these linking agents in each of the four phases I judge important in any technology transfer: decision, acquisition, innovation, and diffusion.