Included in the group is Garcia's 19-year-old daughter, the future diva Mme Malibran, later renown for her wide vocal range and dramatic passion. They tour in NYC, culminating their stay with a performance of an oratorio to thousands gathered in the sanctuary at Old St. Patrick's Cathedral. The result is magic, planting the seeds of a love of opera in the hearts of New Yorkers.

Present day, Mott and Prince Street, New York City. Jared Lamenzo, organist at Old St. Pat's, finds a program for a long-lost oratorio performed at his church in 1826. Reaching out to Italian musicologist Francesco Zimei, Jared and Francesco piece together the music and work with an Italian opera company, Teatro Lirico di Cagliari with Donato Renzetti conducting, to recreate the event. Starring along with the opera company is the Erben organ, a 150-year-old treasure in need of repair and possibly making its last major performance.

Hosted by Martin Scorsese with insight from church parishioners as well as comedian Jim Gaffigan and his wife Jeannie, "The Oratorio" is a documentary about the roots of opera in New York City. It also is a historic look at Little Italy, home to the church for over two centuries, and examines the role immigrants have played in shaping the community, bridges between the old world and new, and the beginning of a cultural awakening in America.