Despite growing attention to framing contests as important discursive struggles in articulating societal challenges and their solutions, most research focuses on competition over which frame becomes dominant. The process of how macro-level master frames themselves are subject to processes of meaning elaboration is less well understood, yet central for understanding field dynamics. In this paper, we focus on how a master frame – seen as relatively stable macro-level meaning structures – can itself get co-opted, such that it is reinterpreted to support a logic of action that is contrary to the original set of meanings. Using a mixed methods approach, combining topic modeling with qualitative analysis to examine the German nuclear energy media debate, we explore the hostile takeover of the dominant and socially resonant “security” master frame. This led to a complete frame reversal: nuclear energy could now be presented as a solution to security, rather than presenting a significant security threat. We develop a model explaining this process of frame co-optation, which involves broadening the master frame through its infusion with new diagnostic claims with regards to the identification of problems and problem solving-schema, sustaining frame plurality, and then selectively retaining the new meanings while detaching the original meanings.