Meg and Tom Keneally 
The Power Game [EPUB ebook] 
The Monsarrat Series

Murder often comes with an easy scapegoat…
When a boatman is murdered on a remote island off Van Diemen’s Land, the authorities want to blame a famous, and very inconvenient, political prisoner.
In this, the third in the Monsarrat series, Hugh Llewelyn Monsarrat and his trusty housekeeper, Mrs Mulrooney, are sent to remote Maria Island to solve the murder of corrupt tradesman Bart Harefield. When Harefield is murdered with an axe, blame is laid at the feet of Thomas Power, the charismatic Irish revolutionary held in detention. Monsarrat and Mrs Mulrooney soon realise their real job is to tie Power neatly to the crime, so he can be hanged without inciting rebellion.
But were there others who also had reason to want to shut Harefield up?