Yilkuba, witchdoctor of the Sura tribe, reads the omens for Dawiya, his king. He tells the king to beware of war, white magic and "cold water that burns." Meanwhile tin miner Mark Fernandez is under pressure from his company to increase production.

15 miles from the bush hospital at Vodni, Jean Stuart, a nursing sister, finds herself stranded and at some risk from recalcitrant native women who want more money for their efforts. She is saved by Captain Allison, a District Officer en route to his post. Captain Allison offers her his bed at the nearby rest house.

Next morning Fernandez sets out to deliver a shipment of tin. He stops at the inn but instead of meeting Captain Allison, who has gone off hunting, he encounters Jean Stuart doing her morning exercises. Fernandez is highly amused. His next stop is to King Dawiya where he offers him three bottles of 'medicine' a week, in exchange for 200 men to work in the tin mines.

At a social event in Vodni, a drunken Fernandez amuses his drinking partner with the tale of the morning gymnast in Captain Allison's room. Later he makes a pass at Stuart, but is rebuffed by Allison.

Some days later Allison decides to hold a court at his residence for the tribal leaders. The King of Mongu complains that Dawiya and his Sura tribe have attacked his camp and stolen his cattle. Allison goes in search of Dawiya and finds him passed out drunk. He suspects Fernandez is the supplier, and his theory is proved correct when he finds an identical bottle in Fernandez's house. Fernandez tells Allison to mind his own business.

One day at the mines Fernandez collapses in a drunken heap. His stupor becomes a fever and Stuart is asked to tend to him through his illness. Fernandez slowly recovers under Stuart's care.

Meanwhile Allison receives a letter relating to Fernandez. Apparently he is a wanted man operating under an assumed name. The letter directs Allison to arrest Fernandez and hand him over to the authorities.

Stuart feels sorry for Fernandez and asks Allison to help him but Allison refuses, though not revealing the contents of the letter. Later, Fernandez arrives. He claims that the letter is an excuse to stop him seeing Stuart. Fernandez and Allison fight. Stuart angrily sends Allison away.

Fernandez takes alcohol to Dawiya and starts a rumour that Allison plans to put Dawiya in chains and make the King of Mongu their new chief. Dawiya and his men prepare to attack Allison's camp. Yilkuba tries to dissuade Dawiya and, when this doesn't work, sends for help from the Mongu king.

Dawiya and his men surround Allison's small troop. Allison is wounded. The Mongu arrive just in time and chase off Dawiya's men. Allison sets fire to Dawiya's empty village as punishment. Dawiya kills Fernandez. When Stuart hears the full story of Fernandez's treachery, she apologises to Allison for her hasty judgments.