Service-Oriented Architecture (SOA) is a set of practices for architectural design of software that exploits services as loosely coupled components orchestrated to deliver various functionalities. The SOA paradigm is not well established in the Serious Games (SG) domain, but it is expected to provide benefits, particularly in reducing the conceptual and technological complexity of the development. In this paper, we propose and study the application of a SOA approach to SG development. We have used the SOA approach to develop an adaptive Serious Game for teaching basic elements of probability to high school and entry-level university students, called The Journey. Details of the architecture implementation are offered, as well as the results of an evaluation of the system using the Architecture Tradeoff Analysis Method (ATAM). Based on our experience, we argue that the SOA approach can make SG development shorter, more flexible and more focused.