After reading in bed, Imogen starts to nod off, so she asks her lady to mark her page and leave the candle burning. Imogen says her prayers, but once she falls asleep, Iachimo emerges from the trunk that he had said contained jewels for the Emperor.
Before falling asleep, Imogen makes sure to recite her nightly prayers—a show of her piety to the gods, who control human destiny in this play. The visual effect of Iachimo emerging from the trunk creates a shock for the audience, who understand the treachery in Iachimo’s seemingly innocuous request about the jewels.
Iachimo comments that all other people are sleeping and he likens himself to Tarquin (the infamous prince who raped Lucretia in Roman legend) in the way he sneaks quietly across the floor. Iachimo compares Imogen to Aphrodite, and praises her fair skin, red lips, and sweet-smelling breath. He wishes he could kiss and touch her, but instead he takes notes on the room.
By comparing himself to Tarquin, Iachimo adds suspense to the scene. That allusion prompts the audience to fear that Iachimo will violate Imogen—a woman vulnerable and alone. It’s a step further than Iachimo’s attempts to kiss her when she was alone. However, the audience experiences momentary relief when Iachimo announces he’ll take details about the room—the start of the “proof” he’ll bring back to Posthumus.
Iachimo observes the bedchamber’s physical layout and prays that Imogen will stay asleep. He steals the bracelet Posthumus gave her, noting that showing it to Posthumus will drive him crazy. For even stronger “proof,” he takes stock of a mole that looks like a cowslip on Imogen’s left breast. He concludes that this will be the strongest evidence of seducing Imogen that he could offer Posthumus.
Once again, Iachimo prays to the gods as he did when he first saw Imogen. When he fears that he’ll be no match for Imogen (who, if awakened, would cause a stir—unlike the frailty and submission he expects of women), he prays. Stealing Posthumus’ love token makes concrete Iachimo’s theft of the lovers’ trust and happiness. Similarly, Iachimo’s observance of intimate details of Imogen’s body are a violation—he’s not so unlike Tarquin after all.
Having obtained all his proof, Iachimo observes Imogen’s book: she was reading the story of Tereus and the rape of Philomela. Iachimo asks the night to pass quickly, because he is scared of staying in the room—even though Imogen is an angel from heaven, he finds his situation hellish. The clock strikes, and he hides in the trunk once more.
Once again, the allusion to the story of Philomela, who was raped, mirrors the way that Iachimo violates Imogen’s privacy and sense of trust with her husband. Iachimo’s fear may also indicate a pang of guilt. Here, Shakespeare hints that the treacherous Iachimo may be a redeemable character.