Boer War veteran Corben Plath has nothing to lose when the Queensland Coal Board offer him blood money and a ticket on the cruise liner S.S. Yongala. Aboard Yongala, Prof. Portland is traveling with his young niece, Felicity, and his renewable energy invention, the 'Smoke Engine'. Fearing that the Smoke Engine will ruin them, the Coal Board task Plath with murdering Portland. Onboard the ship, Plath strikes an innocent friendship with Felicity, not realizing that she is the niece of the man he has been sent to kill. As Yongala steams into heavy weather, Plath learns that there are armed men aboard looking for him and he comes to see that his own salvation depends on Felicity surviving the storm.