Having been re-captured by Warlock and his gang, the Saint, still posing as 'Amos Klein', accompanies Warlock to Hermetico, the underground building Warlock wants to rob, posing as prospective clients, and making a note of the lay-out. The Saint devises a plan to breach its security and begins to train Warlock's men to raid the stronghold. However disaster strikes when one of the gang recognizes the Saint and his cover is blown. The real Amos is taken hostage on pain of death if the Saint does not carry out the robbery as planned.
—don @ minifie-1