Fire will fall by Carol Plum-Ucci 485 pages

Yes, this is a sequel that requires one to read the first installment: Streams of Babel. It picks up right where the first one ends. The Trinity Four, four kids who survived terrorist poison plot are again targeted by the same terrorist ring. The two geek teens who helped saved them have survived a different poison attempt, but are afraid that their amazing computer skills might turn on them and reveal to the bad guys where they are. So, they quickly come up with a plan to bomb their hide-out. Meanwhile the Trinity Four aren't sure whether their bodies have successfully fought the viruses. Moved to an old mansion donated by a sympathetic professor, they fight many inner demons. The bioterrorist threat seems real. Cora is a bit whiney, but otherwise the teens are well drawn.