After a distinguished service in both the armed forces and then the police, leaving the latter when he felt that the criminals seemed to have more rights than their victims Greg Kingston joined an import/export company based in London but whilst checking the accounts uncovered a massive fraud which he was being implicated in.Whilst working overtime one week-end he is injured in an explosion outside his office building and learns it was carried out by a universally acclaimed assassin known simply as The Seven of Hearts because that playing card is always left at the scene.The killer has crossed his path once before whilst in the police and though desperate to know the true identity of the perpetrator is unable to because of his injuries and has to recuperate in Almeria where he meets Francesca who reignites his love for life, but on his return finds that his ex-wife has been gruesomely murdered by a hired hit man who was himself killed right afterwards.As Kingston looked into her affairs he found out that she had been a high-class prostitute even whilst they had been married and soon realises that she had been killed because of something she had seen or heard and one name, Freddie Glover, soon comes to the fore. Racked by guilt over her death Kingston vows to exact revenge on those he felt responsible and is surprised when further investigations prove to him that the company fraud and her murder are connected and that Freddie Glover is someone from his past.He has to use all the experience gained whilst in his previous occupations in order to find out who had his wife killed and for what reason and along the way receives help from a number of unexpected sources, namely an old army friend and a mysterious guardian angel who seems to be following and protecting him.Before he can speak to those he thinks hold the keys to his wife's death they themselves are eliminated until finally he comes face to face with Freddie Glover and learns that friends and enemies can often be one and the same.