One of the main concerns of a French prison guard over the course of their day is to delegate the task of socially reintegrating incarcerated persons and watching over their safety to other professionals. At night, however, the various contributors and providers of those services leave the prison premises, and this “dirty work”—as the guards generally refer to it—falls to those on night shift. When the “dirty work” can no longer be delegated to someone else, three, polarized attitudes to inmate guarding come to light. The first, which I call the strictly statutory attitude, amounts to simply refusing to assist inmates with reintegration in the interests of preserving oneself and one’s sleep. In direct contrast to this kind of professional disengagement, we find what I’ll call two different senses of mission. The first, which I call the security mission, involves the idea that the prison population is not vulnerable—another widely-held understanding—but dangerous, and that, left to their own devices, they would use the night hours to engage in illegal practices. In direct contrast, the second mission, that of “care” (a reference to the concept of “care” developed by English-language ethicists, psychologists, and feminists), consists in accepting to assist inmates with reintegration and protecting them when they are most vulnerable—during the night hours—as a way of morally ennobling the occupation of prison guard. As guards are not really trained in reintegrating inmates, they draw on their own socialization to find a response to the nocturnal fragility of incarcerated persons and situate themselves preferentially with regard to one of the three attitudes. I try to analyze some of the regularities that may be observed between prison guards’ own social pasts and the attitudes they adopt on night shift.