Barty Gunliffe, the farmer's son, is exploring the remote corners of Malachi's Cove in search of seaweed. He's searching the outer rocks, where Mally ordinarily wouldn't go. She's not pleased that Barty seems to think that he can find seaweed where she can not. This is Mally's domain, not Barty's, and she resents the presence in her cove of someone she considers an arrogant interloper.
Be that as it may, Mally still has a decent soul beneath her rough exterior. She may resent Barty, but she doesn't mean him any harm (despite the fact that she actually tells him that she hopes he will drown). So she warms him about a particularly dangerous whirlpool among the rocks. Yet despite this warning, poor Barty slips and falls into the pool. It looks for certain that he will die, but Mally, at great risk to her own life, comes to the rescue and bravely saves the hapless farmer's son.
Barty's head has been bashed about by the rocks, and he's unconscious. But thankfully, he's alive. Although some of the locals believe that Mally tried to murder Barty, the truth comes out when Barty regains consciousness. The first word he speaks is "Mally," and he and the forlorn, lonely waif fall in love.