The play is composed of seven vignettes. The first takes place at a union meeting of taxi drivers, where union boss Harry Fatt tries to dissuade the men from striking. A few drivers ask of the whereabouts of Lefty, their elected chairman. Fatt reminds them their elected committee is already present, then lets Joe, one of the drivers, speak. Joe says that he is not a "red boy", citing his status as a wounded war veteran, but complains that any driver who expresses dissatisfaction with working conditions is labelled a "red" (slang for communist) by the bosses. He says his wife has convinced him to strike for higher wages.
In the second vignette, set a week before that union meeting, Joe comes home to find that his furniture, not yet paid for, was repossessed. Joe's wife Edna urges him to lead a strike and demand a living wage. Joe argues that strikes do not work and that he would lose money while on strike. Edna criticizes the union as benefitting only its leaders. Joe admits the union bosses are "racketeers" but refuses to stand up to them. Edna announces she is going back to her old boyfriend, since he earns a living. Joe protests, and Edna implores Joe to start a workers' union without the racketeers. Joe, swept up by her passion, tells her he is going to find Lefty Costello.
The next vignette features Fayette, an industrialist, and Miller, a lab assistant. Fayette raises Miller's salary as a reward for his loyalty, and reassigns him to a new laboratory where Miller will help create poisonous gas for chemical warfare. Miller loses enthusiasm, but Fayette believes the world is on the brink of war, and that the U.S. must be ready. Miller grows distraught, reminiscing about his brother who died in the previous war. Fayette expects Miller to provide a weekly confidential report on the project's leader Dr. Brenner. Miller refuses to do any "spying", insisting he would rather lose his job than agree to such terms. Miller's outrage grows and he punches Fayette in the mouth.
In the fourth vignette, Florence tells her brother Irv that she loves her boyfriend Sid. Irv urges her to break up with Sid, since he earns too little money as a taxi driver. Sid enters and Irv exits. Sid says he knows he is like "rat poison" to her family and knows that she is reconsidering whether to marry him. He laments their lowly status as "dogs" under the thumb of powerful rich men. He is upset that his brother, a college boy, has swallowed the "money men's" propaganda and joined the navy to fight foreigners who are, ultimately, just like himself. Florence says she will follow Sid anywhere, but he tells her to be realistic.
Back at the union meeting, Fatt brings up Tom Clayton, who took part in an unsuccessful strike in Philadelphia. Clayton says that his experience taught him that Fatt is right about not striking. Clayton's brother runs into the meeting and identifies Clayton as a company spy who has been breaking up various unions for years. Clayton leaves and his brother voices skepticism of Fatt's claimed ignorance of Clayton's true identity.
The next vignette occurs in the hospital office of the elderly Dr. Barnes. The younger Dr. Benjamin enters, upset that he has been replaced for surgery on a patient in the charity ward by an incompetent doctor named Leeds, the nephew of a senator. Barnes reveals that the hospital is shutting the charity ward because it is losing money. It is also firing some staff, including Benjamin. Though Benjamin has seniority, he is being fired because he is Jewish. Barnes takes a phone call and learns that the patient has died in surgery. Benjamin is furious, saying he was skeptical of the ideas of radicals until now, and vowing to fight on even if it means death.
A man named Agate talks to the taxi drivers, insulting their weakness and insulting Fatt. Fatt and his armed guard try to detain him, but Agate eludes them. Agate says that if "we're reds because we wanna strike, then we take over their salute too!" He makes a Communist salute. Agate incites the drivers with fiery rhetoric about the rich killing them off. He tells them to "unite and fight!" and not to wait for Lefty, who may never arrive. A man runs in and reports that Lefty has just been found, shot dead. Agate yells to his fellow union men, "Workers of the world... Our Bones and Blood!" and leads them in a chorus of "Strike!"
