A review copy was provided by the publisher in exchange for an honest review. Portal 24 by Meredith Stroud is a fast-paced, globe-trotting novel full of fight scenes, hilarious and kick-ass characters, techie stuff and time-travelling. Is 24-hours enough, to save the world?As a con-artist, Darius Simms was a keen observer and knew when a person was bluffing him but when Agent Grosz told him that he and his girlfriend will die that evening, he didn't know what to think. Soon he finds himself agreeing to be a replacement field agent to a team of special teenagers whose goal was to prevent catastrophic event from happening.Less than a day after he settled in his new home at Project Oberon and meeting his four teammates, a cataclysmic event happened in New York city that destroyed almost the whole city and killed millions of people. The team will go back 24 hours before the event happened and stop it from occuring, this time. But as soon as they time-travelled back, Darius and the others realized that someone knew that they were coming and he prepared a not-so-welcome party for them. They only have 24 hours to find the destructive device in 4 different places around the world, diffuse it and go back to the present. Easy, right? Not so much. Can they complete the mission or will they die trying? I really liked the characters in this book, they talk, act and think like a real teenagers. I also liked that each of them have their own field of expertise. Constance is the wheelwoman/mechanic, Leon is the hacker/medic, Malik is the sniper/marksman, Bianca is the expert in combat and tactics, and Darius, well, he's street-smart, expert in deception and redirection. They're like a dream team of some sort and I must admit, they're quite badass.The storyline was adrenaline-pumping intense. So many fight-scenes, explosions and running here and there, and you know how much I loved that. My only concerns were the explanation of the science stuff was a bit confusing. I didn't completely understand the train explanation and the reason why you can't go forward after 24 hour limit. Also the ending was so abrupt. Not like a cliffhanger-style ending but like winning a tough battle of videogame then seeing a poorly-made victory message at the end. No fireworks, no special effects, just a "You Won!" message. Yeah, it was a bit disappointing hence the rating. If it doesn't have a sequel then an epilogue would have helped in wrapping it all up especially since there's still a few loose ends left hanging.Overall, it was still a fun and entertaining read. Will still recommend it to everyone especially to kids who love sci-fi and action.