Director Richard Lester uses the Burt Shevelove/Larry Gelbart/Stephen Sondheim Broadway musical hit as a launching pad for some of his wildest slapstick gaggery. Zero Mostel repeats his stage role as Pseudolus, the cunning Roman slave who'll do anything to win his freedom. The plot hinges on three Roman houses next door to each another.
One is the home of Pseudolus' masters: the philandering Senex (Michael Hordern), his domineering wife Domina (Patricia Jessel), and their handsome but empty-headed son Hero (Michael Crawford. The second house is a brothel belonging to unctuous procurer Lycus (Phil Silvers).
The third house has long been empty, in that its owner, the senile Erronious (Buster Keaton), has gone on a long journey to find his children, who were kidnapped in infancy by pirates.
Other principals include Pseudolus' fellow slave, the aptly named Hysterium (Jack Gilford); vain warrior Miles Gloriosus (Leon Greene), who marches triumphantly into Rome declaring I am a parade!; and the virginal Philia (Annette Andre), a resident of Lycus' domicile who is loved by Hero but who has been promised in marriage to Miles Glorious.
There are also acrobats, transvestites, a phony funeral, and an outsized climactic chase.