Foreshadowing is a literary device that can be employed to give readers and audience members hints at what is to come. Foreshadowing can be created through "imagery, language and/or symbolism" ("Foreshadowing," Literary Terms). While foreshadowing only implies what will happen in the future and "does not directly give away" what will happen, foreshadowing can be subtle or more direct. The editors of Literary Terms give us an example of more direct foreshadowing in which a business woman leaving for work declares she has forgotten something at home and a camera zooms in on a USB stick. The camera zoom directly implies that she will soon realize she has left a very important USB stick at home, which will lead to a future conflict.
Early in Euripides' play Medea, the Nurse certainly gives us some very direct foreshadowing about what is to come. The first instance of direct foreshadowing is found in her opening monologue in which she fills the reader in about the background details concerning the story and relates her fears that Medea will either murder her children or murder her husband Jason and his new bride.
The second instance of direct foreshadowing is seen when the Attendant brings the two sons home after playing sports. The Nurse and the Attendant talk about the rumor that Creon may banish Medea and both her sons. Then, the Nurse tells the children to enter the house and tries to put them at ease by saying, "[A]ll will be well." Next, she begs the Attendant to prevent the children from going near their mother and makes the following observation:
For ere this have I seen her eyeing them savagely, as though she were minded to do them some hurt, and well I know she will not cease from her fury till she have pounced on some victim.
As we see later on in the play, Medea certainly does murder her sons with her sword as a means of seeking revenge against Jason. Therefore, the Nurse's warning that Medea may harm her children certainly serves as an instance of direct foreshadowing.