Reverend Michael Hill (Edward Herrmann) and his two children arrive in a fictional California town. He is there to serve as the new minister at the North Avenue Presbyterian Church. The secretary/music director for the church, Anne (Susan Clark), is wary of the changes Hill intends to implement. Hill wants to get people involved, and asks Mrs. Rose Rafferty (Patsy Kelly, in her final movie role) to handle the church's sinking fund.
On his first Sunday, Hill learns from Mrs. Rafferty that her husband Delaney (Douglas Fowley) bet all the sinking fund money on a horse race. Hill delivers a sermon less than 15 seconds long, then rapidly escorts Mrs. Rafferty out the church as astonished worshipers watch. She leads him to the bookie, hidden behind a dry-cleaning shop, and meets Harry the Hat (Alan Hale, Jr.), who recommends that Hill let the bet ride. Hill's horse loses and he is thrown out of the betting parlor. Hill summons the police, but the booking joint has been skillfully removed.
That evening, Hill delivers a tirade against the organized crime in the city during a local television broadcast. He is chastised by his presbytery superiors for the tirade, and is urged to go out and build church membership in the area. His only success is with a rock band called Strawberry Shortcake, who he recruits to "jazz up" the music at church; Anne resigns as music director. Then, two treasury agents for the US government arrive: Marvin Fogleman (Michael Constantine) and Tom Voohries (Steve Franken). They want Hill to help them close down the gambling racket by recruiting some men from the church to place bets that the agents will watch. Hill cannot find any men to help, but hits upon the idea of using women. Five women from his congregation (and Delany, whose wife does not drive) attempt to place bets in the company of the Treasury agents, but with disastrous clumsiness.
The team changes tactics to try to go after the "bank" that the gangsters use, tailing the mob's deliverymen through town while Hill coordinates using a map at the church office. Two gangsters subsequently appear at the church during services and identify the women.
Anne discovers the operation, even as Hill defends the Irregulars as keeping the gangsters off balance. Anne resigns from the secretary position, and soon after, the gangsters bomb the church.
Hill is shocked at the gangsters' act, and seems ready to give in, but to his surprise, Anne wants to join the fight. They do so, and continue to hammer the gangsters' movements around town. Meanwhile, Hill receives word that the pulpit has been declared vacant and North Avenue will be discontinued as a church entity.
Dr. Victor Fulton (Herb Voland), a representative from presbytery, arrives to discuss the closure with Hill. Anne picks up two more presbytery representatives at the airport, but while bringing them to the church, she recognizes one of the mob's deliverymen and realizes she may be able to find the bank. She tracks the deliveryman to an isolated compound. Within minutes, all the Irregulars besiege the place as the gangsters attempt a frantic escape with their bank. A demolition derby ensues, the crooks are stopped, and the evidence is seized.
The following Sunday, Hill's congregation gathers outside the gutted church while he delivers news of the indictments against the mob and of the closing of the church. However, Dr. Fulton steps in to proclaim that North Avenue has a new lease on life—it will be rebuilt. The youthful band starts the music again as everyone rejoices.Edward Herrmann as Rev. Michael Hill
Barbara Harris as Mrs. Vickie Sims
Karen Valentine as Jane
Susan Clark as Anne Woods, Church Secretary
Cloris Leachman as Claire Porter
Douglas Fowley as Mr. Delaney Rafferty
Patsy Kelly as Mrs. Rose Rafferty
Virginia Capers as Cleo Jackson
Herb Voland as Dr. Fulton, Head of the Presbyterian Executive Committee
Ruth Buzzi as Dr. Rheems
Michael Constantine as Marv Fogleman
Steve Franken as Tom Voories
Carl Ballantine as Sam the Tailor
Alan Hale, Jr. as Harry the Hat
Frank Campanella as Max Roca
Don Stanley as TV Announcer (Uncredited)
Melora Hardin as Carmel
Bobby Rolofson as Dean
Marjorie Bennett as Mother Thurber
Ceil Cabot as Bench Woman