Outside of Jason's adopted house in Corinth, a nurse recounts and laments the chain of events that have lead to the present crisis in the city, where Medea's "world has turned to enmity" (line 15). Jason and the crew of his ship, the Argo, began this history by sailing to Colchis, a city in Asia and Medea's home, in search of the legendary Golden Fleece. Medea, a sorceress and princess, fell in love with Jason, used her magic to help him secure the Fleece, and eventually fled with him to Iolcus, Jason's home. There she continued to use her magic and to participate in intrigues within the royal house, eventually tricking the daughters of a rival king, Pelias, into poisoning their own father. After accepting sanctuary as exiles in Corinth, Jason and Medea had two children, now young boys, and achieved a degree of respectability, earning them a "citizens' welcome" (line 12) in the city. Recently, however, Jason has abandoned Medea and his own children in order to remarry with Glauce, the daughter of Creon, king of Corinth. Jason hopes thereby to advance his own station, perhaps even to succeed as king.
The nurse's lament expresses an impossible desire: to undo the past. Medea, Jason, the chorus, and others will replay their own versions of this futile wish at various stages in the play. Jason and Medea each express remorse at having inaugurated the events the nurse recounts here; their past love has doomed them in the present.
Tragedy, as an art form, often imparts a very basic message: actions, premeditated or not, bear consequences that must be recognized and endured. A great deal of drama simply revolves around a hero or protagonist suffering through his or her actions and generating a perspective in relation to them (think Hamlet). Medea, however, is a play that conspicuously lacks any such self-conscious recognition of error by its characters; no one develops a mature perspective on his or her own actions. As the nurse reveals to us, Jason abandons Medea on a whim. Although this abandonment precipitates disastrous results to himself and all those surrounding him, Jason never acknowledges his responsibility for the suffering he has created. Like the nurse here, he simply wishes things had never happened. The predominant mood of the play is denial, and the nurse's tone in these opening moments resonates with everything that will follow.
The story of Jason and the Argonauts was already well-known to Euripides' audience, perhaps second in popularity only to Homer's accounts of the Trojan war. In keeping with Euripides' overriding themes, the nurse selects only those elements that echo with the succeeding action, particularly Medea's cleverness, guile, and willingness to sacrifice connections to family and kingdom in order to pursue the flights of her passions. Unlike Jason, who uses deceptive rationalizations to avoid facing the consequences of his own actions, Medea simply rides her passions unthinkingly. Even before Creon banishes Medea, she is already a perennial exile, unconcerned with the chains of responsibility that bind her. The most visible signs of abandoned responsibility are Jason and Medea's children; shuttled around the stage, used in a murder plot, and then murdered themselves, their silent characters will be masterfully handled by Euripides as testimony of the play's most significant absence--accountability. Thus, the nurse's opening lament establishes both the tone of denial and theme of lost accountability that pervade the entire play.