Frank Peretti's novel This Present Darkness is an attempt to weave realistic fiction and elements of the supernatural, specifically angels and demons, together into a cohesive plotline that reveals the existence of the spiritual realms and the importance of spiritual warfare.

Set in the small town of Ashton, the story mainly follows two main characters: Marshall Hogan, who is the editor-in-chief of the local newspaper, and Hank Busche, who is the pastor of a small but faithful church. Both of these characters face opposition—such as false allegations, temptations, interactions with demon possession, family problems, and arrest—as they seek after truth when they recognize changes coming into their town.

These changes stem from the purchase of the community college by a New Age group called The Omni Organization, which is seen as the operating agent for the forces of evil in the novel. As Marshall and Hank continue to investigate this organization, they uncover that it has strong influence over many major figures in the town, including the police chief and many professors at the community college, and that it plans to extend in its reach once it purchases the college.

However, the two main characters also grow in their faith as they are continually faced with conflict. Marshall, who did not claim religion at all at the beginning of the novel, converts to Christianity, and Hank becomes stronger and more confident in his faith.

Juxtaposed with the human characters is the account of spiritual warfare that occurs between angels and demons as the people of Ashton simultaneously struggle for power. These actual battles between the angels and demons often align with plot points of difficulty for the characters. At the end of the novel, through the power of the prayers of the faithful in the town, the angels are able to defeat the demonic powers and stop the purchase of the college.