"Speak with the man in charge," he said, a smile spreading across his face. This suggests that the speaker is directing someone to communicate with the person in authority, indicating a situation where authority or decision-making is important.
Billy then popped his head inside to see the mayor, Francis Delaney, sitting upright in bed with a sheet wrapped around him. The scene is set as the mayor appears to be resting but alert, possibly involved in a serious matter as the story unfolds in James Patterson's "The Black Book."