AustLit

'In this the third of Boothby's Dr. Nikola novels, Nikola applies his almost hypnotic persuasion to convince an out-of-luck Australian, formerly from England, named Gilbert Pennethorne to assist Nikola unwittingly in an evil scheme. Nikola takes advantage of Pennethorne's intense desire for revenge against a former boss in Australia who stole information about the location of a gold field that would have made Pennethorne immensely wealthy.

'Using that information the boss made himself rich, living a high life in London, while Pennethorne remained penniless.

'Bob Wentworth, 18, and Jack Armstrong, 16, leave their work at the Clyde Engineering Works and set off to Australia with Mr Mackay in search of gold. The story moves from the goldfields of WA across the centre of Australia. The character of Mackay is based on Macdonald himself. He is engimatic, an able fighter, and a sensitive flautist who has a broad general knowledge (which he is not averse to imparting freely) and is moved to tears by music.'

(Oxford Companion to Australian Children's Literature 271).