When he first arrives on the island, he is physically shackled with no chance of survival, dehydrated and hallucinating about someone long dead.
Turns out that he lives, much, much longer than he expected to (now he understands the English phrase 'be careful what you wish for').
When she arrives on the island, she's just had one invisible shackle broken (a bus accident and a glass of drugged orange juice dotting the way), not realizing that a new shackle has just been clamped around her ankle the moment she shakes Ben's hand.
(The island has a fickle way of keeping them chained right where they don't want to be.)
The island also has a fickle way of forcing him to clean up Ben's messes.
That's why he's here again, sweeping up the shattered remains of glass while Juliet sniffles on her couch, eyes red and raw from sobbing her eyes out for the God only knows time.
It's their own personal vicious cycle, him of them needing (wanting?) to fix her other's messes, creating that almost-but-not-quite atmosphere hanging in the room.
She has her 'arrangement' with Goodwin and cat-and-mouse game with Ben; he has the distant memory of Isabelle. It would never work.
(She just wants to go home; he's completely forgotten the meaning of the word.)
Two days later, he asks Ben to go to the mainland and check on Juliet's sister. Surprisingly, he says yes. It's his version of saying if you need anything, I'm here.
One plane crash, two turns of the wheel and three years later, Juliet never gets to thank him.
He can safely say that this has the first time he has been continuously haunted by a ghost he can actually see.
She appears to him night after night, eyes filled with tears and clothes bloodstained, asking him the same question over and over.
"All I wanted was to go home, Richard," she pleads, blue eyes piercing his soul, "Why didn't you let me go home?"
He blinks and she's gone, trees swaying where she stood and Miles giving him a quizzical look as they press on.
(Needless to say he doesn't have a good night's sleep until he leaves the island.)
In the end, he does find her sister and nephew, tells them everything about what happened during those six years that she was missing, finally gives the brunette woman who looks absolutely nothing like her sister something that seems like closure.
As he's leaving, caught by an unexpected downpour, he swears he hears her voice, sees her smile.
Thank you, Richard.
(She fades away with the rain.)