A dilemma faced by an increasing number of investors is whether to boycott environmentally damaging businesses or whether to enter into a dialogue with them. This predicament now has its epicentre in Cambridge, England, where the ancient university faces great pressure from students and staff to respond to the threat of climate change. Having already received two reports on its approach to responsible investment, the university has appointed a new chief investment officer (CIO) who needs to consider the question of whether to divest or to engage. What would be the financial effects of each choice, and what would be the outcome in terms of environmental impact? Our case describes the background and the research behind the debate. The new CIO and her recently-appointed colleague, the chief financial officer, will present their ideas to the university. In contrast with other Journal articles, we do not propose solutions. Instead, we ask you, the reader, to consider the arguments and to take a position.