William Turner, in most cases, is not an idiot. Will knows plenty of things, in addition to being skilled in a great many, useful areas. He has fought things he had no likely chance in winning against and won against them, and for the most part he has performed admirably, honorably, taking everything in stride, because that's the kind of man he is.
When Will sees Elizabeth kissing, shamelessly tongueing their sea-turtle-roping, rum-drunk Captain Jack Sparrow, for example, Will knows it's started out as something and changed into something completely different, that all three of them might have had a purpose at some point but not any longer. Will's not entirely fatalistic - in fact he usually likes to be optimistic about things - but he knows when he sees beginnings and the ends of beginnings. Fate, the dark side of it, lies in meeting his own father on the Flying Dutchman of all places. Fate may not be death and it may not have anything to do with the heart of the sea but Will knows his father is doomed to be somewhere far below him crushed and water-logged, smothered with barnacles, at least temporarily. And when Elizabeth touches Jack Sparrow, when Jack's water-and-rum-tarnished fingers trace the imperial curvature of her jaw, Will knows she's gone. He knows this and they don't, but it's an unspoken rule that anything Jack touches comes back to him. And stays.
This sets the tone for their stay with Tia Dalma. When asked, Elizabeth says, "Yes," like she's dying of thirst, guilty or grieving or gung-ho or something, and Will doesn't know what any of it means, really, what makes the black liquid come out of Tia Dalma's mouth or how they've ended up with Gibbs again, but "the ends of the earth," sounds like where they're headed anyway. Secretly, Will thinks back to his wedding day and is glad, really, really glad, it was raining.
But he loves her, oh, God, does he love her. He loves her more than Jack could ever love her but in a different way, a way that isn't good enough anymore. He guards her in the night despite the looks given him by Barbossa, by the others. He guards her though she doesn't need him to, and watches her chest rise and fall evenly in the dim light. And just as Will can never rid himself of her, Elizabeth never rids herself of Jack's compass, even though Tia Dalma has asked for it back. He saw her lie. Clutch her hands behind her back protectively. But although the seer-woman must have known it, she understood something else about Elizabeth's heart. Tia Dalma was Jack's too, after all.
One night before they leave Will creeps a bit closer to Elizabeth's makeshift cot toward the compass-that-only-points-north. Will doesn't know everything about the compass, doesn't really understand it, but what Will knows is that when Elizabeth holds it in her sleep sometimes he can hear it move, and wants to know where it's pointing. Will is not the type to give up easily and so he'll wait for her, he'll follow the ex-dead Barbossa to what could likely be another death for all of them, because that's the kind of man Will really is, but Will holding Jack's compass has only ever produced steady results, linear. Resolute. Unchanging.
Will doesn't know where the compass is supposed to be pointing when Elizabeth holds it so firmly in her hand even in sleep, because it doesn't point anywhere. He watches her eyelids flutter and thinks of lips on lips and then Jack's death or pseudo-death, mind leaping to conclusions and through hoops and questioning, and flips the lid on the long-cradled box to watch the needle spin and spin.
