If Only I Knew Then is the fourth and final novel in the series that began with Nursery Rhymes, They Never Saw It Coming, and Vengeance Is Mine. Shean O'Brien is on a relentless path of vengeance, driven by the tragic deaths of his younger twin brothers, who were shot while trying to run a roadblock in Northern Ireland by the British Army. Adding to his fury is the torture he endured at the hands of the police after being arrested twice. Using his cunning, O'Brien has managed to escape their grasp – but his thirst for retribution remains unquenched. Will O'Brien succeed in his mission? And how many lives will be lost in his pursuit of justice – or vengeance?