This longitudinal mixed-methods case study aimed to explain why a seemingly ordinary U.S.-affiliated hyper-connected French language learner (Nancy) achieved extraordinary outcomes after 15 weeks in Paris, compared to fifteen Generation Z peers also enrolled in the program. Framed by Complex Dynamic Systems Theory and social pedagogies, the study adopted a retrodictive approach to "explain after by before" and retrace Nancy's complex, non-linear trajectories of success. Adapting to new realities of students going abroad with their smartphones in hand, multiple measures of success (linguistic, intercultural, social, psychological, emotional) were triangulated with reports on smartphone usage, rich interviews, and background data to provide dense time-series and narrative illustrations of changes. Findings revealed the importance of the activation of Nancy's agency to take advantage of the affordances of her study abroad environment through the butterfly effect arising from her initial conditions, judicious smartphone usage, and quality of L1 and L2 interactions.