Many fluid mixtures exhibit retrograde behavior, including those that define natural gases. While the behavior is well understood for mixtures in the bulk, it is not in nanosize porous space that dominates shale formations in unconventional reservoir. The lack of experimental data urges modeling works to make estimates as best as they could due to immediate needs in gas recovery. However, such efforts have been straying without firm guidance from systematic studies over what we have known so far. This paper is intended to present the results of such a study that would incite further investigations in this area of research. Revisiting the retrograde behavior in the bulk is appropriate to start with, followed by a short review of what we know about fluids confined in nanosize pores. Based on these, implications on the behavior of confined mixtures in retrograde region can be inferred. The implied features that have been supported by experimental evidence are the location of the confined dew point and bubble point at low temperatures, which both at pressures lower than their bulk counterparts. Another feature found in this study is completely new, thus still open for further investigations. It reveals that the dew-point and bubble-point curves of confined mixtures end at moderate pressures on a multiphase curve, beyond which the equilibrium occurs among the bulk and confined phases. The well-known points in the bulk retrograde region, i.e. the critical point and cricodenbar, are consequently absent in confined mixtures.