In this Man vs. Nature story, a determined owner of a coffee plantation is convinced that he can prevent a plague of ants from devastating all that he has worked so hard for on his settlement. Around three sides of his plantation, Leiningen has had a ditch made as a defense against ants. The ends of this "horseshoe" run into the river, and at the end near the house and the outbuildings, there is a dam by means of which the river's water can be diverted into the ditch. In addition, Leiningen has a concreted "inner moat" constructed; into this moat, Leiningen has petrol piped in as a further deterrent for the ants, making "an impassable protection for the besieged and their dwellings and stock."
When the army of ants marches upon the plantation, "shoals of ants" are carried away by the current into the middle why they drown. But, others use the dead bodies as stepping stones. So, a peon is sent to the weir to dam the river and thus increase the speed and power of the water entering the ditch. Before this can happen, however, the ants get across the ditch. Nevertheless, the stronger damming of the river begins to have an effect.
Visibly the swiftness and power of the masses of water increased, swirling into quicker and quicker movement its living black surface, dispersing its pattern, carrying away more and more of it on the hastening current.
It is then that "[V]ictory had been snatched from the very jaws of defeat."