Of course—without proper education due to her illness (her supposed illness), of course Miranda would not know. Indeed, Robert had been part of this lapse even if he had not realized it, long having sought to shelter his 'poor sister' from the evils of the world. This realization, though, was too much on top of a situation that was already too much, and would have to be grappled with later.

"The Imperius Curse," he explained, volume dropping so instinctively that Robin did not even realize it, "is one that strips its target of their will—no," the wizard corrected himself with deepening frown lines, "that's not quite right. It-it binds the target's will to that of the caster, making their person an extension of the caster. Indeed, they can still go about their daily life much as usual, with the caveat that the caster can make any... changes to behaviour, to living, that they so choose."

It was a highly theoretical explanation for an illegal, and now deeply personal, spell.