The eighth book in the H.I.V.E. series, published in 2013.
Otto and Raven are desperate to rescue their friends from the clutches of Anastasia Furan, head of the evil Disciples organisation. First they must track down the location of the Glasshouse, the prison where Furan trains children to become ruthless assassins. But Otto is also being hunted. The past three months that Otto has spent away from H.I.V.E. have given the Artemis Section an opportunity to locate him. The Artemis Section is an elite division of the American intelligence services that specialises in capturing the toughest targets. They report only to the President, which is very bad news for Otto.