When we last left Outcast, Kyle's sister had been possessed by what we assume to be demons. It's easy to make this assumption because the Reverend John Anderson has spent his entire life performing exorcisms to remove them from the bodies they steal. The Reverend sees everything from a biblical perspective and is unwilling to consider any other angle which frustrates Kyle.
Over time and by questioning Sydney and the possessed, Kyle has figured out that the entities which are taking over humans in the town are drawn both to him and his daughter, Amber, who has inherited her unique abilities from him. Allison became possessed because the entity was attracted to Amber's light. Kyle is only beginning to piece things together. Despite all of the years that Anderson has spent supposedly performing exorcisms, he knows next to nothing about the invaders.
Just as in the show, Anderson is quite an arrogant asshole. Anderson is absolutely resistant to the idea that he isn't doing God's work. When he is presented with evidence, like the fact that Maurice is just as affected by Anderson reading the phonebook, as when Anderson read the biblical passages to the other afflicted, Anderson decides that God must have somehow imbued his voice with the holy spirit. Anderson even discounts the fact that regular water seems to work just as well as holy water. At the center of Andersons's angst is the idea that he is isn't important and that he's lost his family for nothing. Kyle is determined to experiment and then learn from each interaction while Anderson looks for away to explain away the evidence in order to centre himself and his faith. It's telling that Anderson refers to God as an asshole when he begins to come to the realisation that he isn't the centre of everything. Anderson's faith is based on his own desire for power and a feeling of superiority more than anything else.
It's clear now that Sydney is the leader of the beings which are controlling the humans. Sydney talks about a great merge that is coming and he clearly sees Kyle as a threat because of course, Kyle can excise the beings. What is it about Sydney that makes him the leader and what is his ultimate goal? The merge implies that everyone in the small town is going to have a creature inside them. We know that the creatures are attracted to Kyle's light but they can still come through without that.