The reason why Dino is black cat with red fur is because he's a unique bi-color cat.
A romantic foreshadowing: Zoe is nicknamed "Princess" by Jeanne, her mother and Nico. Guess what happens? The two get married.
The climax of the story is the cathedral and the French cathedrals usually have gargoyles; these creatures are known to protect people from evil. Costa and Nico are standing on gargoyles when they duke it out. Not five minutes later, Nico is saved (with Jeanne's help) and Costa falls to his death.
What was Costa going to do to Zoe after he and his junkies were done celebrating? Had Nico and Dino not come to save her, Zoe might have had the same fate of her father.
Costa's dead body.
The implications surrounding the death of Zoe's cop father. First, how exactly did Zoe come to know Costa was the murderer of her father? And then there's her status as the Cute Mute. Judging by this evidence, one horrific and sad theory is asked: Did Zoe witness Costa murder her father?