Hide & Seekchronicles the intimate and intensely personal war between Nazi SS Obersturmbanführer for Rome, Herbert Kappler, and Monsignor Hugh O'Flaherty of the Vatican, a fiercely fought rivalry that would culminate in failed attempts by Kappler to kidnap and then murder his Irish opponent. O'Flaherty had decided to quietly resist and fight the new rulers. Dubbed “Ireland's Oscar Schindler,” he masterminded a large-scale operation from within the Vatican, to help Jews and escaped Allied prisoners on the run from the Nazis. He used a series of safe houses and church buildings and sheltered around 500 Jews in the Holy See, and it is believed that sanctuary was found for some 4,000 Jews across Rome, and 4,000 Allied escapees.

After the Resistance killed 32 German soldiers in a bombing, an enraged Hitler instructed Kappler to draw up plans for revent. Eventually, 335 people would be executed in the Ardeatine Caves, a labyrinth of tunnels outside the city. The massacre would become the worst atrocity committed on Italian soil during WWII. Kappler's handiwork remained secret until Rome was liberated. The Nazi Colonel was found guilty on all the charges relating to the massacre and sentenced to life imprisonment. Amazingly, O'Flaherty continued his relationship with Kappler, visiting his former rival in prison and beginning a discussion that culminated in Kappler becoming a Catholic who was baptised by the Irish Monsignor.