It is almost two years since Lacklan walker, veteran Captain with the British SAS, helped Carmen Vazquez escape from the clutches of the Sinaloa Cartel in Arizona. He never expected to hear from her again, and he certainly never expected to hear from her brother. So when Lacklan receives a text message claiming to be from Charlie Vazquez, saying that he is in New York, that his life is in danger and that he needs help, Lacklan is intrigued, to say the least.

But when Lacklan gets to New York, the mystery only deepens - and the more he investigates, the deeper it gets. Charlie has vanished without a trace, and so have his closest friends: Zack the mathematical genius whose brain works with the speed of a computer, Bran whose memory is beyond photographic, and Hans and Hattie, whose powers of empathy and analysis seem almost supernatural.

Who are they? Where have they gone? And what have they done with Charlie Vazquez…?

And then again, who is Dr Olga Lucia Salcedo - The extraordinarily beautiful lecturer at Columbia university, whose relationship with Charlie seems to have been more than just mere mentoring…?