When a batch of contaminated cholera vaccine is stolen in Pakistan, Interpol expect it to be sold on the black market and issue an alert for any to be tested before use. Duval flies to Delhi after the death of a doctor at a small clinic, beaten up but infected with cholera - from a broken microscope slide. As more reports of cholera cases arrive, it appears that a respectable drug wholesaler is the source. Duval suspects if not the company, certainly someone working within it, and must track down all the stolen vaccine before any more is used.