Enter Ophelia.
LAERTES Let her come in.
How now, what noise is that?
O heat, dry up my brains, tears seven times salt
Burn out the sense and virtue of mine eye.
By heaven, thy madness shall be paid with weight
Till our scale turn the beam. O rose of May,
Dear maid, kind sister, sweet Ophelia,
O heavens, is’t possible a young maid’s wits
Should be as mortal as an old man’s life? (4.5.151-159)
Perhaps Ophelia is unrecognisable at first, perhaps she’s being restrained (and the text is messy here; Laertes’s first line might be a printer’s error); whatever, Laertes is shocked to hear and then see his sister. How now, what noise is that?What’s going on? He cannot comprehend, cannot bear what he sees: O heat, dry up my brains—the sun, or even the heat, perhaps, of choler, anger, bloody revenge; act, don’t think—tears seven times salt burn out the sense and virtue of mine eye, let me weep so intensely, so violently that I can no longer see. This is unthinkable, unbearably painful to see. What’s happened to his sister? By heaven, he swears, thy madness shall be paid with weight till our scale turn the beam. I will avenge you too, your state and whatever, whoever has brought you to it; I’ll pay them back so far in excess of whatever it is they’ve done that the scales of justice are completely unbalanced, overturned. Someone will pay for this! O rose of May, sweet, beautiful girl, dear maid, kind sister, sweet Ophelia—my SISTER—but then, rather than asking what’s wrong, who did this, what’s happened to you, it’s as if Laertes steps back and starts to understand the sheer bloody unfairness of life, another Hamlet moment, and perhaps with more cause: O heavens, is’t possible a young maid’s wits should be as mortal as an old man’s life? Is sanity that fragile? Can everything in my life, everyone I love, fall apart and be taken from me, and from themselves, with such easy swiftness?
Near the beginning of the scene, it was mostly to himself that Claudius referred when he lamented that when sorrows come they come not single spies but in battalions—but it’s Laertes and Ophelia to whom that’s most applicable here.