Doctor Burnet (Portman), a scholar of ancient history at the British Museum, is obsessed with finding the legendary and priceless Golden Mask of Moloch, believed to be buried in the lost tomb of a Roman general somewhere in the Algerian desert. He plans his latest expedition of discovery, but lacks funds to pay for an archaeologist to accompany him. He learns from the museum curator that Nicholas Chapman (Heflin), an American author of popular archaeology books, is eager to go along and work without pay, on the understanding that he will be able to publish his experiences in magazine articles and book form. Burnet is dubious of Chapman's expertise and good-faith, but finally agrees to let him join the party.