Synopsis by Hans J. Wollstein
Boris Karloff played a red herring in this the final silent serial from chapter play specialist Mascot, who reportedly spared all expenses this time around. Helene Costello, a former Warner Bros. star now down on her luck, starred as Dorothy Rogers, the daughter of a banker (George Periolat) who disappeared mysteriously while reading a novel entitled "The Fatal Warning." The vanished Rogers was accused of absconding with 100,000 dollars in cash and Dorothy hired private investigator Russell Thorne (Ralph Graves) to clear her father's good name. Suspects abounded, of course, including bank president John Harmon (Tom Lingham), a clerk (Karloff), the inevitable butler (Sid Crossley), a two-bit femme fatale (Symona Boniface), and sundry other nefarious types, all of whom proved to be innocent. In the tenth and final chapter, "Unmasked," Thorne discovered that Rogers had been guiding the investigation from his hiding place and the identity of the real culprit was revealed. Since The Fatal Warning appears to be among the lost, we may in good conscience reveal his identity here as well: seemingly stalwart businessman Leonard Taylor (Phillips Smalley). In addition to the presence of a pre-Frankenstein Boris Karloff, The Fatal Warning is also noteworthy for an early appearance by future Three Stooges foil Symona Boniface.