Nora O'Brien leaves Ireland to visit her brother in America. On the trip she suffers a concussion, and soon is mistaken for another Irish girl named Nora who is on her way to visit her aunt in the US, Mrs. Watson, who has not seen her niece in many years. Nora, still somewhat dazed from her injury, is taken to the Watsons' home, and when Mrs. Watson's son Jack returns from college, he falls in love with her but cannot express it to her because he believes she is his cousin. Complications ensue.

Mary Randall, who has just lost her job, is taking care of her widowed mother. Mary learns that her late uncle has left her part of his estate. She and her mother move to Florida to live on the Twisted Oaks Plantation. Mary meets her neighbor, Jack Carleton, and the two fall in love. The workers on the plantation believe in voodoo. The Voodoo Priest incites the superstitious workers. Mary orders him off the plantation, and he vows revenge.

This play is enacted during the stormy days when Robert Emmett tried vainly to free Ireland. Con Daly loves Nora Doyle, who lives with her mother in a little cottage amid the hills and dales of old Erin. In a cave nearby the men who would free Ireland are making arms and ammunition. Robert Emmett visits them, and then goes into the enemy's camp disguised as a flute player, and returns safely. The constabulary visits a family and a riot starts, and as a result Major Kirk is shot. Desperately wounded, he is taken to the home of Mrs. Doyle. Nora and Con nurse him back to health.

Eileen Donaghue loves Myles Murphy, a match which is approved by Mrs Donaghue. Colonel Reid of the British Army employs an informer, Fagin, who has designs on Eileen, but Myles gives him a beating for his presumption. As a result, Fagin tells Reid that Myles is plotting against the Crown.

The wide-ranging storyline of The Melting Pot takes its characters from the Jewish ghettoes of Russia to the Lower East Side of New York.