On Mrs. Olesen's invitation, a charismatic, dynamic preacher named the Rev. Edward Danforth comes to Walnut Grove. He is quite the evangelist, and even better, he does more ... much more than just preach the Word of the Lord.
The hynotic Rev. Danforth, you see, actually bears witness to God. As dramatic organ music is played, he intones he is a faith healer. And how effective is his work? Well, watch as he helps a crippled man to walk. Feast your eyes on the blind woman who, with a few simple commands, can now see. Wow! If he can do that, well, he can heal any sickness, just by asking God.
Eventually, Rev. Alden's simple Sunday services seem just that – simple and outdated. Both Rev. Alden and Dr. Baker worry about Rev. Danforth's charismatic preaching and ability to convince Hero Township residents of his "healing powers." Charles has also attended one of the preacher's revivals, but has rejected his ministry.
Dr. Baker has also told Rev. Danforth what he thinks of his so-called "healing" powers, that they don't exist. But word spreads of the unflattering remarks, and Dr. Baker's practice suffers.
Later, a farmer brings his teen-aged son to Rev. Danforth. The boy is suffering from severe abdominal pain, and places his complete trust in the faith healer to make it go away. Dr. Baker – who is sure the boy's appendix is rupturing and needs surgery instead – happens to watch Rev. Danforth place his hands on the boy's stomach ... and the pain goes away. "He's healed!" Rev. Danforth exclaims, and a disbelieving Dr. Baker is discredited.
Rev. Danforth suggests a joint pastorship to stop a possible exodus from the Walnut Grove Church, but Rev. Alden declines the offer. In return, Rev. Danforth schedules his Sunday revivals and Wednesday prayer meetings at exactly the same time as Walnut Grove Church's services. Just as Rev. Alden fears, nearly everyone – save for the Ingalls, Garveys and Dr. Baker – go to hear Rev. Danforth instead.
However, Dr. Baker is later proven right about the boy's appendix, which bursts and results in his death. The farmer is angered and outraged and goes to the prayer service to demand answers. Rev. Danforth belittles the man, and literally forces him to admit that God "chose" to take his son home with Him.
Charles learns that Rev. Alden is considering resigning from the Walnut Grove Church after losing his congregation to an apparently superior preacher. Charles begs his friend to reconsider, but a proud Rev. Alden snaps at him.
Rev. Danforth, feeling satisfied about his work, decides to spread his ministry in towns throughout southern Minnesota. After he leaves, Nels (who had initially welcomed Rev. Danforth and had gone, partly due to his curiousity) begins having second thoughts about the new pastor, and admits to Mrs. Olesen that he felt pressured to help her extend an invitation.
Charles is on a delivery run to Sleepy Eye. That night, he overhears Rev. Danforth's revival and the voice of the "blind" woman begging to have her sight restored. Charles confirms his suspicions when he walks in and sees the preacher at work: the woman is pretending to be blind, and the "crippled" man is also acting. Everything is clear now – Rev. Danforth is a charlitan who uses actors and actresses to fool others into believing he really is a faith healer.
Charles listens to Rev. Danforth, and then asks someone where he'd be preaching next. He doesn't say anything, but instead formulates a plan to expose Rev. Danforth at his next revival in another nearby town. He gets the Olesens, Dr. Baker and the father of the boy who died to go with him to the upcoming revival. Charles had also wanted Rev. Alden to go, but when Rev. Alden declines, Charles agrees that if they were to show up together and levy their accusations, Rev. Danforth would claim it to be part of a scheme to get him to leave.
Just before Rev. Danforth gets into the heart of his preaching, Charles hatches his plan. The boy's father confronts Rev. Danforth with his accusation, but the preacher claims he doesn't know him. Charles then backs up the father, and has Dr. Baker and Mrs. Olesen identify everyone involved with the scheme. He exposes the actors by taking the faux-cripple's crutches and swings them at the "blind" woman, and then says that Rev. Danforth's ministry was built on lies. The congregation begins to walk out.
In the end, the Walnut Grove residents – the lost flock who strayed and are now repentant – all return to Walnut Grove Church, to partake in Rev. Alden's simple, old-fashioned ... but effective, joy-filled and wonderful services.
Rev. Alden is touched, and then admits to his friends and congregants that he was filled with envy and jealousy when Rev. Danforth came to town. After all, he wanted to be a "fire-and-brimstone" preacher in a large cathedral, but this whole situation made him realize he was meant to be a simple country preacher. Everyone forgives him.