This directed case study in PowerPoint format focuses on the London Underground Mosquito, Culex molestus, and its potential relationship to the common mosquito, Culex pipiens, in order to explore the topics of evolution, reproductive isolation, and speciation. As the story unfolds, the case mirrors the process of science. The students receive some initial data and observations collected by researchers Byrne and Nichols in London. Based on these observations, the students then form a hypothesis and design an experiment. Finally, they receive more data collected by Becker et al. and draw conclusions. At the end of the case, the students are able to reflect on the importance of the iterative nature of scientific investigation.  In addition to using clicker questions and small group discussions, this case is also "flipped"; before coming to class, students prepare by watching several short videos that teach the basics of speciation and mechanisms of evolution, including a video created by the author on cladograms and two species concepts. Originally written for an introductory biology class, the case could be used in a majors, non-majors, or mixed-majors setting.