I started to learn a lot more about two characters in particular- Hazel and Leo. Though they are not the main characters in the book, Hazel and Leo are still very significant in the plot. Both have a very important role in as for they are two of the seven people who are destined to stop Gaea from taking over the world. In many ways, Hazel and Leo are very alike. One way is that they both had very dark pasts- Hazel was resurrected from the dead by her brother and Leo had a harsh aunt who put him into foster care and was really mean to him. Also both have a encountered Nemesis, who is the Goddess of Revenge, and she told both of they about their responsibilities or fates that are going to occur in the future; Hazel has to go and rescue Nico, for he will die in six days, and Leo is the odd man out and he will need to fight through many hardships in the future. No that I have declared them to be quite similar, I think that Leo, who actually thinks that he is the odd man out will realize that he is not really that different from Hazel and he might stop those thoughts from contaminating his brain.
I think that Nico, Hazel's brother, will be saved by Leo, because during the mini quest to get materials for the ship, both Hazel and Leo develop a friendship. And with that friendship, Leo will feel obliged to save Nico. Though there is not too much evidence to back up that prediction, I surely think that Leo will rescue Nico. That prediction is for later in the book, but for now, I think that after Leo and Hazel return to the Argo II, the other will be back and they will head to Rome to save the entire Rome as well as Nico. This can be thought through logic; if they cannot head back to the Roman demigod's camp and they have nothing really to do at Camp Half-Blood, their only other option in order to advance their plan to stop Gaea and go to Rome.
I think that at the end of the book, the Roman demigods will realize that some took control of Leo, who made him attack the Roman camp. Since the Roman are following them, I think that both of the groups will travel to Rome and, meet there. However, they will later realize that Leo was being controlled by someone else. So far, I think that this a great book and encourage everyone to read this series.