In the opening of the film, Kolchak is sitting on the bed of a sleazy hotel room, dictating a book into his trademark portable tape recorder. The book is about a series of unusual events in Las Vegas, and a cover up of those events by the authorities. He describes a series of murders that had plagued the world-famous Las Vegas Strip. All of the victims had their blood drained, and Kolchak comes to suspect that the killer believes himself to be a vampire, much to the chagrin of his cantankerous boss Anthony (aka Tony, Antonio) Vincenzo, portrayed by actor Simon Oakland. Kolchak also has a girlfriend named Gail Foster (Carol Lynley) who earns her living as a dancer. During the movie, Kolchak attempts to get her to give up her night job, though he does not offer her a proposal of marriage, or other commitment. At the urging of this girlfriend, Kolchak begins to look into vampire lore, but is skeptical. When a meeting is conducted with the sheriffs department, the DEA, the police and others they discover the suspects true identity named Janos Skorzeny who is the prime suspect in multiple homicides extending back years involving massive loss of blood. When the murderer is robbing a hospital the police arrive trying to stop him and even by shooting with guns but he escapes outrunning a police car and motorcycle.
Inexplicable events lead Kolchak to begin to believe that something supernatural is occurring, and the evidence of his own eyes eventually persuades him that this is in fact a real vampire. Kolchak is able to convince the police that they are fighting a vampire when failed capture attempt happens with the suspect possessing incredible strength and not slowing down when shot repeatedly, but Kolchak ultimately destroys the vampire and unlike subsequent productions, he does so with the help of his friend in the FBI (a credible eyewitness).
Kolchak writes his version of the story for the newspaper, and proposes to his girlfriend, telling her that they will both move to New York City. However, in quick succession, the authorities print a false version of the newspaper story, with his byline, and threaten to charge Kolchak with first degree murder unless he quietly leaves Las Vegas. Kolchak is told that his girlfriend Gail has also been "asked to leave town" for engaging in unsavory activities, and has already been forced to leave the city. Carl exhausts his savings placing personal advertisements across the country in an attempt to find her but is unsuccessful.
The final scene is of Kolchak in the sleazy hotel room, finishing his book. He explains that if anyone tries to verify the events described in the book, they will find that everyone involved has either left town or is not talking and there is no file on the suspect and all of the evidence has been destroyed by the authorities, and all of the bodies cremated.
Is Kolchak able to convince the police that they are fighting a vampire?
Yes