In 19th century England, a noted brain surgeon rescues a former student from being hanged on a false conviction for murder, and spirits him away to an ancient, repurposed abbey far in the countryside. There, he connives his pupil into assisting him in mapping the functions of the various parts of the human brain, using living subjects who are under a terrible animation-suspending drug called "black sleep". Subsequently, the student, along with the daughter of one of the subjects, discover that most of these subjects have survived but are being kept in a dungeon-like cellar, in various stages of physical and mental derangement...

War heroes Rip Murdock and Johnny Drake are sent to Washington, D.C, to receive top honors for their service. Johnny, seemingly terrified by the publicity that awaits him, jumps off the train and later turns up dead. Suspecting foul play, Rip begins digging into his pal's past. He encounters cover-ups, threats to his own life and deadly femme fatale Coral Chandler.

Army Lieutenant Halliday, accused of stealing the Army payroll, pursues the real thief on a frantic chase through Mexico aided by the thief's ex-girlfriend and is in turn being chased by his accuser, Capt. Blake.

Career gambler Dan Milner agrees to a $50,000 deal to leave the USA for Mexico, only to find himself entangled with fellow guests at a luxurious resort and suspecting that the man who hired him may be the deported crime boss Nick Ferraro aiming to re-enter to the USA.