In the flashback scene when Nucky is turning Gillian over to the Commodore,he holds out his hand to her.

That single gesture results in the end of Gillian's innocence and the beginning of Nucky's deal with the devil.

When he visits Gillian in the lockup,Nucky has one final chance to try and atone for what he did.

Instead, he once again takes her hand,and once again,leaves her alone and doomed to a hellish existence.