i love the seven going off on their quest together, and the entire time they're together pre-tartarus, every so often one of the others catches percy and annabeth having a conversation, and they'll see them both turn to face empty space, stop talking, and then continue with slightly sadder, more melancholic tones.
and nobody talks about it, nobody asks questions, because maybe it's just them readjusting after nine months of being apart?
but there's something missing from percy and annabeth. there is something just slightly off about their interactions. they love and adore each other, that much is obvious, but every interaction is slightly sad, not perfectly happy.
and it's not until the end of the battle at camp half-blood, when there's a sigh of relief, and the air is full of hope, when percy caps riptide and reaches out to take annabeth's hand, and the silence is broken by a single voice screaming their names, and everyone watches a satyr come flying across the battlefield, his arms reaching towards percy and annabeth before he's even close enough, when percy and annabeth immediately step forward to catch the satyr, who sobs into percy's shoulder and clings to them both and can't stop rambling that they're alive, when percy grips the satyr's shoulder a little too tightly, and annabeth lets her shoulders fall
and for the first time since meeting the couple, jason, piper, leo, hazel, and frank watch as their unofficial leaders let go of their need to protect, the need to be on guard, and fall apart in the arms of their protector, that they realize what had been missing.
it wasn't a feeling, an item, or an emotion.