Timeriders Timeriders Series, Book 1.

Liam O'Connor should have died at sea in 1912. Maddy Carter should have died on a plane in 2010. Sal Vikram should have died in a fire in 2029. Yet moments before death, someone mysteriously appeared and said, "Take my hand . . ." But Liam, Maddy and Sal aren't rescued. They are recruited by an agency that no one knows exists, with only one purpose - to fix broken history. Because time travel is here, and there are those who would go back in time...