The play is set in the era of the 5th-century Roman Republic. The Roman people are rioting because of food shortages, with citizens complaining that the patrician class who governs the senate are hoarding all of the resources while the plebeian class starves.

The Roman patrician Menenius Agrippa appears before the mob. The citizens do not harm him because he is considered friendly to the common people. Menenius attempts to calm the rioting crowd by telling them a parable about the human body. He describes how many parts of the human body began to resent the belly, thinking that it did nothing but receive all of the food. However, the belly explained that it served only as the storehouse, distributing the food to every functional limb and organ of the body, down to the most insignificant part. Menenius compares the belly to the senate and the rioting limbs to the people.

Caius Martius, another Roman patrician, enters and scolds the plebeians for rioting. He insults them, calling them cowards because they do not serve as soldiers. Speaking with Menenius, Martius is furious that the senate has been forced to concede to the crowd’s demands, granting them five tribunes to serve as their representation in government.