In 1968, a staid yet respected Southern California pastor, Chuck Smith, finds that his church is slowly dying with an inability to connect with the younger, live-free generation of hippies. One day, his daughter, Janette, gives a ride to a colorful hippie hitchhiker named Lonnie Frisbee, who says he is traveling around and telling people about the Ministry of Jesus. Smith, at first suspicious of Frisbee, eventually warms up to him and welcomes other hippies to his house. They join forces and start a successful movement to evangelize hippies and others.
Meanwhile, high-school student Greg Laurie runs away from his Junior Reserve Officers' Training Corps class and joins a girl named Cathe who "turns him on" to a rock concert featuring Timothy Leary preaching the value of drugs for self-discovery. However, Greg sees that various hippies are dangerously irresponsible; Cathe's sister gets sick from a drug overdose. Greg and Cathe find solace at Smith and Lonnie's ministry, though Cathe's uptight parents are not enthusiastic about Greg.
The ministry explodes in popularity, being seen as a "Jesus Revolution" or "Jesus freaks", and even sparking a Time magazine cover in 1971. However, Lonnie becomes egotistical and eventually splits with Smith, though they reconcile later on. Greg offers to take over a ministry branch in Riverside, and eventually marries Cathe and becomes a famous pastor himself. Smith and Frisbee are remembered as founders of the widespread Calvary Chapel movement, and more generally as leaders in the Jesus movement.