After sneaking into Imogen’s bedroom by hiding in a chest, Iachimo makes close observations about her body in order to deceive Posthumus into believing that he has slept with her, thereby winning their bet by cheating. In this scene, Shakespeare alludes to the myth of Tereus and Philomela. Watching Imogen as she sleeps, Iachimo notes that:
She hath been reading late
The tale of Tereus; here the leaf’s turned down
Where Philomel gave up. I have enough.
To th’ trunk again, and shut the spring of it.
Swift, swift, you dragons of the night, that dawning
May bare the raven’s eye. I lodge in fear.
Though this a heavenly angel, hell is here.
Iachimo observes that, before falling asleep, Imogen had been reading “the tale of Tereus,” putting down the book at the point at which “Philomel gave up.” Shakespeare alludes to the story of Tereus and Philomela, which was well known in Renaissance England. In the myth, a woman named Philomela is raped by her sister’s husband, Tereus, who cuts off her tongue to prevent her from accusing him. By alluding to Tereus and Philomela here, Shakespeare connects Iachimo to an infamous rapist from mythology. Though Iachimo does not literally rape Imogen, Shakespeare suggests that his violation of her boundaries in sneaking into her room and gazing at her body while she sleeps is a form of assault. This allusion also foreshadows later events in the play. Just as Philomela is able to get revenge against Tereus, so too will Imogen be offered a chance to reveal the truth and redeem herself.
In a moment of grim comedy punctuated by dramatic irony, Imogen unknowingly foreshadows later events in the play. When Pisanio attempts to moderate her excitement about Posthumus's apparent return to Britain and suggests that they could travel no more than 20 miles in a day, Imogen responds impatiently:
Why, one that rode to's execution, man,
Could never go so slow: I have heard of riding wagers,
Where horses have been nimbler than the sands
That run i' the clock's behalf.
Imogen argues that Pisanio is underestimating how quickly they can travel to Milford Haven, where Posthumus has asked her to meet him clandestinely. An individual being driven “to’s execution,” she argues, would still go faster than 20 miles a day. Imogen’s morbid joke relies upon the assumption that someone being driven to their execution would likely want to move as slowly as possible in the hopes of gaining time and delaying their death.
However, Imogen does not understand just how well this example applies to her own situation. Posthumus’s letter was part of a murder plot, as Posthumus has arranged for Imogen to be killed on the way to her destination. Her offhand comment about execution, then, foreshadows her later discovery that her husband intends to murder her as punishment for what he falsely believes to be her infidelity to him.
Posthumus awakens after listening to the argument between the ghosts of his family members and Jupiter, chief god of the classical pantheon, which he perceives at first as a mere dream. As he awakens, however, he discovers that there is a mysterious “tablet” lying on his chest. The cryptic prophecy inscribed upon the tablet foreshadows the ending of the play. He reads the text aloud and then comments upon its contents:
Whenas a lion’s whelp shall, to himself unknown,
without seeking find, and be embraced by a piece of
tender air; and when from a stately cedar shall be
lopped branches which, being dead many years, shall
after revive, be jointed to the old stock, and freshly
grow, then shall Posthumus end his miseries, Britain
be fortunate and flourish in peace and plenty.’Tis still a dream, or else such stuff as madmen
Tongue and brain not; either both or nothing,
Or senseless speaking, or a speaking such
As sense cannot untie.
Posthumus cannot decipher the cryptic message, which he dismisses as yet another dream, or otherwise, the “senseless speaking” uttered by “madmen.” Unable to decide whether or not there is any meaning in the words, he resolves to keep the tablet just in case. Though he cannot make sense of the prophecy, it accurately foreshadows the ending of the play. Posthumus, whose surname is “Leonatus” or “Lion’s son,” is the “lion’s whelp” of the prophecy, fated to “be embraced” by his beloved Imogen once he has given up looking for her.
Additionally, the “stately cedar tree” of the prophecy represents the royal bloodline of Cymbeline. Just as the tree of the prophecy will “revive” after its “lopped branches” are “jointed” back to its trunk, so too will the royal family thrive after its own missing branches (Cymbeline’s two long-lost sons) are reunited. At a dark moment in the play, the prophecy promises a good fortune for Posthumous, for Cymbeline, and for Britain, foreshadowing the play’s happy ending.