Iron Maiden has been both criticized and praised for their unforgiving presentation of hard rock. This album took them to worldwide stardom, and awoke accusations of backward masking, subliminal messages, and Satanism. Producer Martin Birch dissects the master tapes with the five band members, who discuss the writing and recording of each song, while looking for the 'hidden' elements.

The 1972 early metal classic is examined here. After a brief recount of Deep Purple's history prior, all five members of the group from that time recount the making of the album, and Jon Lord, Richie Blackmore, and Roger Glover isolate some of their parts, and play along live. Engineer Martin Birch also lends a hand, describing how the instrumental sounds were produced.