One evening as the P. and O.'s vessel "Neptune" steams away from Australia to Britain, Ronald Monteith, a young, wealthy Australian is taken into the confidence of a fellow-passenger Lionel Ventin who relates the story of his rather tragic life. When Ventin is found stabbed to death in his cabin the next morning Monteith vows to find the murderer, thinking it must surely be the vengeful wife of whom he spoke who is responsible. When arriving in London he immediately seeks the help of a barrister and a detective. However, as he delves deeper into the mystery, he is mortified to find the evidence begins to point to the girl he has fallen in love with - the girl from Malta... - Summary by Celine Major