In the last book, as a recap for anyone who didn't read it, Alex and Kol had met.
They didn't exactly have a great relationship with each other until later in the book.
They had admitted their feelings towards each other and then Jessica had killed Alex and Caleb killed Jessica.
Then Elena and Jeremy had killed Kol.
In this book, Alex is annoying Caleb and he's trying everything in his power for her to regain her humanity.
Will he succeed or will she still have no humanity for the rest of her time on the Other Side and drive Caleb into doing the unspeakable?