Oliver Whyte is found murdered in a hansom cab in Melbourne. Brian Fitzgerald (Arthur Shirley) is arrested for the crime and brought to trial, but is acquitted at the last minute by Sal Rawlin, a missing witness who produces an alibi. The mystery involves Brian's fiancee, Madge (Grace Glover).
The film details Australian contributions to flying, including the feats of Lawrence Hargrave, an early flight of Harry Houdini in 1910, T.E. Hart's flight from Sydney to Penrith, Guillaux's 1914 flight in Sydney, the work of Ross and Keith Smith, and Australian flying inventions. It then covers the history of Sir Charles Kingsford Smith and his plane, The Southern Cross, in particular his circumnavigation of the world. It also touches on the development of the Australian postal air route.