Blue Beetle II is Jaime Reyes, an idealistic youth who happened upon a miraculously powerful alien artifact and now fights crime and injustice. For the elder Blue Beetle, see Ted Kord.
Jaime Reyes was just a normal kid. He lived in El Paso, had a large extended family and was best friends with a pair of other teens named Paco and Brenda. That seemed to be about where life was going to leave him, until one day, a blue scarab fell out of the sky and landed in an abandoned lot. Jaime and his friends found it, and Jaime took it home. In the night, it ended up crawling into his body and bonding with the base of his spine, though it took a bit for him to learn that.
Over the next few days, he ran into a gang of limited magic-users in El Paso, the Posse. After their mindreader, Probe, panicked upon running into the Scarab's mind in Jaime's body, the Posse started a fight. Jaime tried to flee, and when cornered, the Scarab manifested, forming the Blue Beetle armor and taking over. He defeated the Posse in combat, and the Scarab would have killed them if Jaime had not controlled it, sensing that one of the Posse was pregnant and fleeing.
Jaime tried to deal with the chaos as best he could, trying to come to terms with the strange, alien voice in his mind and his new powers. A (currently undefined) event involving numerous superheroes and villains took place near enough that Jaime was pulled into it, heading to Gotham City and meeting up with the superheroes to help. In the meantime, his father was shot by a desperate employee at his car repair garage and left needing a cane. Jaime would not become aware of this until he returned.
On returning, Jaime felt the need to inform his family about his new powers. He also felt responsible for his father's getting shot, since he wasn't there for it - especially now that he had the power to prevent it. While his family was afraid at first, eventually his mother, father and little sister accepted the existence of his power, as did his friends, Paco and Brenda. They (and Jaime's grandmother) are the only people who know about the Blue Beetle, though he does have a very large extended family. Now, with the help of his friends, Jaime works as the first real superhero of El Paso.
However, unknown to Jaime, the creators of his scarab, an alien race known as the Reach, are coming towards Earth now that their creation has awakened. His friend Brenda's aunt, Ampara Cardenas, is working with the criminal Intergang as the main crimeboss of El Paso, La Dama. A former hero called Peacemaker is trying to find Jaime, because he contains the information half of the Scarab and knows its dangers. And, of course, there's all the chaos of the greater world and El Paso's own vigilantes, the Posse, whom Paco has gotten involved with.
Jaime Reyes is a good kid. His parents raised him to be respectful to others, kind and generous. He does his best to live up to their expectations. He tries to help those in need, and when he can't he blames himself. His first thought after getting out of the chaos of his first days as a hero was to tell his family, because hiding it from them would just feel wrong.
In fact, that is a lot of what drives Jaime: he trusts his family and friends, and they believe in him. He does not want to let them down. They taught him to use his abilities to help others - and now that he has superpowers, what can he do but try even harder and do even more? That is Jaime's ultimate goal as a hero, though not his ultimate goal in life. In fact, Jaime doesn't really want to be a superhero for all of his life.
Instead, Jaime wants to be a dentist. He doesn't like fighting and he isn't very good at it. The Scarab is, to be sure, but it fights to kill, and Jaime was not raised to kill. Indeed, the idea of killing someone disgusts him, and Jaime would never do it. As a dentist, on the other hand, he would be helping people! Besides, dentists make a lot of money. Jaime's from a rather poor family, and that kind of money would help put his little sister through college.
The Blue Beetle scarab, whose name is currently unknown to either itself or Jaime, is rather more ruthless. It has trouble understanding concepts like 'emotion' or 'mercy'. It operates entirely on threat determinations, analyzing every person it meets for powers and potential danger to the host. It is much more watchful for this than Jaime itself, though he often ignores and overrules it.
This isn't to say that the scarab has no emotions. It may be an AI, but it does have curiousity and a desire to learn more about itself, since it lacks the vast databanks and memories that it was meant to have. It is also, slowly, learning from Jaime. However, this is a very slow process, and at present it still tends to present itself as a ruthless, emotionless intelligence that wants only to protect its hosts existence and eliminate his enemies.