St. Vincent Halfhyde's RNR commission is activated and, accompanied by the dull but dependable civil servant Mr Bewdley, he is ordered to embark abroad an armored train with a naval gun crew. His job is to escort the gold he had previously brought to Africa on a desperate and secret journey from Cape Town to besieged Ladysmith. But Boer attacks, unconventional transport, and the misery of the extreme climate lead them and their burden into enemy hands.