Sir Borotyn, a prominent Prague resident, is discovered murdered in his home, with all indications pointing to a vampire assault. The victim's friend, Baron Otto, and the physician who analyzes the body are certain that the vampire is the mysterious Count Mora, or perhaps his daughter, but receive little help from the law. Professor Zelen, an expert in the occult, is called in to assist with the investigation.

• Metro-Goldwyn-Mayer
• Lionel Barrymore
• Elizabeth Allan
• Bela Lugosi
• Lionel Atwill
• Jean Hersholt
• Henry Wadsworth
• Donald Meek
• Jessie Ralph