The Fall by Robert Muchamore (CHERUB #7)

When an MI5 operation goes disastrously wrong, James Adams needs all of his skills to get out of Russia alive. Meanwhile, his sister Lauren is on her first solo mission, trying to uncover a brutal human trafficking operation. And when James does get home, he finds that his nightmare is just beginning ...CHERUB agents have one crucial advantage: adults never suspect that children are spying on them.