It's a boiling hot afternoon in a rural village three hours' walk from the nearest health centre.
A child is suffering from acute diarrhoea, a common but lethal problem which could be fixed with a simple course of oral rehydration salts, or ORS.
The salts cost next to nothing, but the village's only shop doesn't stock them. Instead it sells washing powder, cooking oil, plastic buckets and the inevitable bottles of Coca-Cola.
Why can one get Coke, but not medicine? And how can a fizzy drink access pretty much every distant village on earth? And how could we learn from that and cover those last, crucial miles to reach that child?
These were questions that British aid worker Simon Berry was asking in a remote corner of north-east Zambia more than 20 years ago.
The answer he came up with was a simple one: a packet of ORS and other medicines that could be slipped in between the rows of bottles - in the unused spaces - in a crate of Coke and transported, anywhere, via Coke's regular distribution routes.
And so the ColaLife "aid pod" was born.
After advertising his idea on the social media, Mr Berry eventually got in touch with Coca-Cola executives to talk about hitching a ride on their supply network.
A surge of corporate and media interest also saw a funding grant from Britain's Department for International Development, while mothers in Zambia helped improved the design of the aid pods.
The same plastic container that was used to protect and transport the contents - the salts, plus a 10-day course of zinc supplements and soap for hand-washing - was also designed such that it could be used to measure, mix and drink the salt solutions.
At the same time, smaller, single-dose ORS sachets were produced with the help of local pharmaceutical company Pharmanova.
The aid pods promise to save many lives - diarrhoea is the second biggest killer of children under five, and according to the World Health Organisation, 760,000 infants die every year of the disease even though it is preventable and treatable.
When New York-based documentary-maker Claire Ward following a field trial last August for her film The Cola Road, she was impressed by ColaLife's creative ingenuity. Her narrator says: "This is a story about thinking outside the box and inside the crate."