Video and computer game users are frequently stated as possessing a higher proficiency in English. In this study, 3 Swedish upper secondary school students from different programs played The Infectious Madness of Doctor Dekker, a lovecraftian murder mystery game. The aim was to examine the possible effects on their English vocabulary acquisition through their ability of assuming words' meaning from the context presented by the game. The words used in the study were low-frequency words which were gathered from the game and then cross-referenced with the Corpus of Contemporary American English(COCA). The 80 least frequent words were selected. Participants were tasked with translating, explaining or using the words in sentences after completing a game chapter. The study found that the game had in general had a positive effect on the participants’ vocabulary store. However, the test scores varied greatly between participants; 1 participant acquired 1 word while another participant acquired 18. This, combined with the small sample size, meant it was difficult to say definitively how effective the game had been at expanding the participants' vocabulary store.