A Royal Abduction - Arthur W. Upfield

Arthur Upfield, creator of the Aboriginal detective 'Bony' followed his classic crime novel The Sands of Windee with this historical romance:

The Crown Prince of Rolandia is visiting Australia - and two brilliant Americans, Earle Lawrence and Van Horton - abduct her on the trans-continental train on the Nullabor Plain. They hide her in caves near Eucla on the Great Australian Bight, until the search is called off and a ransom is arranged...