An eventful and exciting story of a medical gamble in the tropics relies on many divisive interests- personal and professional- and sends Peter Mayne, of the Ministry of Health, to check on Martin Farrell, who is testing (without official approval) his vaccine against encephalitis on the natives of a small island off coastal Africa. Mayne had known Farrell years ago- and theirs had been an uneasy friendship-ending, when out of a sense of obligation, Mayne had left the girl he loved- Barbara-to Farrell. Now, after ten years, he finds that Farrell has not changed- he is still rude, reckless, dogmatic and determined, and that he himself has not changed- he still loves Barbara. Off the island, as well as on, Farrell's test- a double blind (half those injected receive the vaccine- half a placebo) has aroused resistance- and while scientifically more precise, it is riskier. The health center is burned- and Farrell injured and it is up to Mayne to try and pull him through with some chancy surgery... A smooth entertainment relies on many uncertain situations, native versus white, official protocol versus unorthodox corner-cutting, public interest as against private dreams of glory, and it handles its touch and go moments with accomplishment and assurance.