Sure Fire by Jack Higgins

The phenomenally successful Jack Higgins teams up with Justin Richards to launch a sure fire best seller for children. The mother of fourteen-year-old twins Rich and Jade dies in a car crash and they are told they must go and live with their estranged father, who they have never met before. Neither the children nor their father get on, but when Rich and Jade witness him being kidnapped they are drawn into a dangerous crisis that could engulf not just their family but the whole world!