For 16 years, Toby Jones had plodded though life without exerting himself, that is until a letter arrives that turns his whole world on its head. In three eventful days, he changes from a carefree teenager into an intrepid treasure hunter as he is drawn into the hunt for a stash of diamonds that disappeared a hundred years before. A frantic quest to find the diamonds is set in motion when television historian Lucien Blake arrives at Toby's school to film a documentary about missing millionaire Thomas Wenlock. When Toby discovers that Wenlock was his great, great grandfather and he is heir to the missing fortune, he realises he has to beat Blake to the diamonds or lose them forever. With the help of four school associates, he embarks on a journey of twists and turns that grows ever more dangerous as a determined Blake pursues them all the way.