The body of the Portuguese king, Sebastian of Portugal, was never recovered, nor was that of nobleman Dom João de Portugal, of the important House of Vimioso. Madalena de Vilhena, Dom João de Portugal's widow, has since married Manuel de Sousa Coutinho, a chivalrous knight of the Order of Malta. The two lead a virtuous and happy existence, along with their frail young daughter, Maria de Noronha, perturbed only by the silent reproach of a loyal servant, Telmo Pais, the only one who still believes that his former master shall return. Madalena has grown anguished the possibility of Dom João's return would mean her second marriage is bigamous, void, and that her daughter Maria is illegitimate. They live in Manuel de Sousa Coutinho's elegant palace in Almada, and receive word that the Spanish governors have decided to move their quarters to the residence to escape the plague that was devastating Lisbon: in a fit of patriotism, appalled by this arbitrary resolution, Manuel de Sousa Coutinho sets fire to his own house. While they escape, Madalena watches as a portrait of Manuel is consumed by the flames. They are now forced to live in Dom João de Portugal's uninhibited palace. The gallery of the old palace is dominated by a portrait of Dom João besides that of King Sebastian — which Madalena interprets as a grave omen. While Maria and Manuel de Sousa Coutinho are away, Madalena is being settled by her brother-in-law, Frei Jorge, when they receive the visit of an old pilgrim from the Holy Land: he tells them that he was kept in captivity for many years and that Dom João is still alive. When asked who he is, the pilgrim points at Dom João's portrait and replies ""Nobody."" Deathly ashamed, Madalena and Manuel de Sousa decide that the only solution was for them to go their separate ways and each join a convent. Telmo Pais tells Dom João about the frail young Maria de Noronha, and the old nobleman regrets his presence is causing the family such distress and is covering the woman he loved in dishonour: he bids Telmo to go and tell them all that the pilgrim was a fraud, but it is too late — the play concludes as Manuel de Sousa (now, Brother Luís de Sousa) and Madalena take their take solemn vows to live cloistered monastic lives, and the orphaned Maria de Noronha interrupts the ceremony with an emotional and feverish speech about how the social mores have torn their family apart before she succumbs to consumption.