33 Half Moon Street - SA - Killer Killed Twice

A woman named Theresa Mandan seeks help from an investigator, Mr. Mason, to find an escort for an aerial balloon race, claiming her mother is tied up with work. Mason assigns his assistant, Marmaduke "Marmy" Bray, to accompany her but suspects her story may be a ruse. Meanwhile, Inspector Bottomley from Scotland Yard arrives, revealing that Theresa is under surveillance related to a missing man, Grant Webster, who is possibly connected to her family. As the balloon lifts off, Marmy is unaware that Theresa has manipulated the situation, removing the batteries from his walkie-talkie to prevent communication. During their flight, she reveals that they are jettisoning a heavy sack as ballast, which Marmy suspects might contain something sinister. After a series of tense moments, it is uncovered that Grant was actually murdered, and Theresa's mother, Dr. Mandan, was involved in covering up the crime to protect themselves from the real killer, who was poised to eliminate them next. Inspector Bottomley apprehends the actual murderer, leading to a conclusion that intertwines deception and danger surrounding the balloon trip.