Dangerous Diamonds by Barbara Mitchelhill

Random House, 2010. ISBN 978 1842709788
Twins, Harry and Charlie see their father use his mobile phone after they have been to a concert in Edinburgh, but that is the last time they see him. Searching through his study once they arrive back home, they ring his friend, Edina Ross, and she is particularly interested when they talk of what they have found. Their father, a writer, has borrowed a reliquary form the museum to put on the front cover of his next crime novel, and when the twins look at it more closely, diamonds fall from a compartment in the bottom of the small box. But telling Edina seals their fate, and Harry is taken to the country, hotly followed by Charlie, who, after seeing what has happened to him, smuggles herself into the back of Edina's car and so goes to the same hideout.
Action packed, smart and up to the minute, this adventure, crime novel and thriller, all wrapped up into one absorbing tale will have broad appeal with its boy and girl protagonists and a hat full of nasty evil doers, pursued by the crooks, the Russian mafia and other assorted goodies and baddies. With all the thrills of a good TV series, this one is sure to find a home for a minute or two on the shelves.
Fran Knight