Playing computer games is widely popular among children and teenagers as an entertainment activity; meanwhile, playing computer games also provides a learning opportunity. For example, the rules of the game have to be learned by the player in order to improve his/her performance. Based on that principle, the City eHealth Research Centre (CeRC) developed a web game for 13-15 year olds, whereby the player becomes an investigator who attends the scene of an incident that involves microbes. There are four missions in total, each involving a mystery that the player needs to solve and learning objectives that need to be taught - such as antibiotic resistance and the importance of hygiene. This paper presents the results from a game evaluation that took place between July of 2009, in four UK schools (Glasgow, Gloucester, London), with 129 students; whereby 98% of the students commented positively about playing the game. Subsequently, CeRC has improved the game and developed an interactive educational games portal (www.edugames4all.com) for different age groups of web game enthusiasts.