Meanwhile, the initial speech by Polixenes calls attention the fact that he has been in Sicilia for "Nine changes of the watery star"(I.ii.1), which coincides, rather obviously, with the length of Hermione's pregnancy, and suggests that Shakespeare wishes to call attention to the idea of infidelity from the beginning. And when Leontes later says "I am angling now, / Although you perceive me not how I give line"(I.ii.180-81), one can easily imagine that the entire business of asking Polixenes to stay is another "angling," designed to trap the Bohemian king and enable Leontes to dispose of him.
The roots of Leontes's jealousy are uncertain. Shakespeare allows him some of the play's most brilliant, and biting lines—"And many a man there is, even at this present, / Now while I speak this, holds his wife by th'arm, / That little thinks she has been sluiced in's absence / And his pond fished by his next neighbor, by / Sir Smile, his neighbor"(I.ii.192-96)—but refuses to give an easy explanation as to why he is so certain of Hermione's infidelity. The play allows no possibility of her guilt, but he does see her "paddling palms and pinching fingers"(I.ii.116), which (unless we think that Leontes hallucinates) suggest a degree of physical intimacy with her husband's friend. Still, a wide gulf remains between such behavior and Leontes's grim certainty of sexual relations. There is a traditional male fear of illegitimacy at work, of course, as we observe in the king's attempts to see his own likeness in Mamillius's face—in a time when male heirs were critical to dynastic survival, wifely adultery was a great fear, as one could witness with Henry VIII and his execution of multiple wives only a half-century before Shakespeare. At the same time, a number of critics have found a clue to Leontes's madness in the intensity of his friendship with Polixenes, whose depiction of their unfallen, innocent boyhood suggests that they have "tripped since"(I.ii.77) by marrying. "Of this make no conclusion," Hermione protests, "lest you say / Your queen and I are devils"(I.ii.82-83), but the real suggestion is that the closeness of Polixenes and Leontes was so great that it is difficult for the adult king of Sicilia to separate himself from his friend, even now that they are married. "To mingle friendship far is mingling bloods"(I.ii.110), Leontes says, but that is exactly what he does—he feels corrupted, in some odd sense, by his marriage to Hermione, and so he projects his guilt upon his friend, "mingling friendship" too far and so destroying it.