Set in Italy in 1946, the play is centred on Filumena Marturano, a former prostitute who has been the mistress of Don Domenico Soriano for nearly thirty years. When she learns that she is going to be ‘thrown over’ for a much younger woman she pretends to be dying. The priest is sent for and Don Domenico is inveigled into a death-bed marriage. No sooner has the priest married them than Filumena makes a miraculous recovery, with the words, ‘Happy Wedding Day, darling’.

As he reels in shock and anger, Don Domenico vows to make the marriage null and void. He then learns that this brilliant, strong-willed woman has a few more surprises for him. She reveals that she has three sons that she has supported by stealing from him – and that one of them is his, but she will not say which one. He then tries desperately to discover his true son.