Book IV opens three weeks after the birthday celebration. Adam is superintending some repairs at the Chase Farm this day, and toward evening he has to pass through the grove in which Hetty and Arthur have been meeting. As he walks along, he suddenly sees the pair a short distance before him; they are kissing. When they notice his presence, Hetty hurries away, and Arthur strolls casually towards Adam. He tries to pass the incident off with a few casual words, but Adam is furious; now he knows where the locket came from. He berates Arthur for trifling with Hetty's feelings and for stealing her affection from him. Arthur tries to make excuses, saying he meant no harm. He is about to leave to join his regiment (he is a captain in the local militia), and points out that the affair is about to come to an end. But Adam is not so easily placated; "you've robbed me o' my happiness," he exclaims and challenges Arthur to fight. Arthur is unwilling, but Adam calls him a coward and the fight starts. It is soon over, and Arthur lies on the ground unconscious.
After a few moments, Arthur revives. Adam is no longer angry. He brings water, then helps Arthur to the Hermitage, a cottage in the woods which has been Hetty and Arthur's trysting place, and Arthur slowly revives. Adam leaves to get brandy, and while he is gone Arthur hides a woman's kerchief. When Adam returns, he apologizes for judging Arthur rashly but asks for an explanation of his relationship with Hetty. Arthur lies again, saying that it has been nothing but a mild flirtation. He betrays guilt, though, and Adam is suspicious that Hetty's heart has been captured permanently. He demands that Arthur write Hetty a note breaking off the affair if he really cares nothing for her. Arthur unwillingly agrees and promises to put the note in Adam's hands the following day.
