This is a study of Singapore pastors' worldview & understanding of the epidemiology, symptomatology and management of possession behaviour. The pastors' accounts are compared with those from the scientific disciplines, and convergences and divergences noted. Factors shaping both the pastors' and the scientific discourses are examined. The pastors are shown to respond to competing scientific paradigms by reinforcing their two-worlds worldview. They either live mainly in the other world, or in each world at a time, or between the two worlds. Based on theological reflection focusing on epistemology, theodicy & cosmology, the author shows that the paradigm of living in both worlds simultaneously is the most appropriate pastoral response. The theological vision of the coexisting worlds and the pastoral task of unmasking and resisting evil in all its varieties and depths are then discussed.