The film tells the story of Bulldog Drummond (John Howard), a Great Britain officer who, while on a drive with his friend Algy Longworth (Reginald Denny (actor)) and valet Tenny (E.E. Clive), is the first to discover a mysterious suitcase that is parachuted from an aircraft above, minutes before the plane crashes. The case is found to contain the highly explosive chemical hexanite, the plans for which have been stolen. Despite the urging of his fiancee Phyllis Claverling, Drummond is dragged into the mystery surrounding the whole affair, traveling by both train and ship to recover the formula.