The plot was relatively simple. A mystery novelist, played by Denholm Elliott, discovers a plan to murder an American heiress, played by Elizabeth Taylor in an uncredited role, while on vacation in Spain. He enlists the help of a taxi driver, played by Peter Lorre, to travel across the Spanish countryside in order to thwart the crime. Some scenes were designed to highlight the Smell-O-Vision's capabilities. In one, wine casks fall off a wagon and roll down a hill, smashing against a wall, at which point a grape scent was released. Other scenes were accompanied by aromas that revealed key points to the audience. The assassin was identified by the smell of a smoking pipe, for example.
The screenplay was adapted from the 1947 novel Ghost of a Chance by Kelley Roos, the pen name of husband and wife mystery writers Audrey Kelley and William Roos. The novel was set in locations in New York City. Kelley Roos also wrote a 1959 paperback novelization of the screenplay, reset in Spain.