David Burke uncovers the clandestine activities of Patrick Crinnion, a Garda intelligence officer who secretly served MI6 during the early years of the Troubles. As the Garda Síochána launched a manhunt for the Chief-of-Staff of the IRA, Crinnion found himself playing a crucial role in the effort to track him down. Before his disappearance, Crinnion's actions exposed a web of secrets including those of another British spy in the Irish police, damaging intelligence leaks, gunrunning by Irish politicians, and a cover-up related to the murder of a Garda. Burke reveals MI6's shady dealings, from attempts to smear Irish politicians to plans for using criminals as assassins and the secret surveillance of a key IRA member. Crinnion fled into exile. The Puppet Masters not only reveals what became of him but also provides an insightful look into a turbulent period marked by covert operations, betrayal, and the power struggle that shaped modern Irish history.