Sir Edward Pellew, captain of HMS Indefatigable decides to put his protégé, Horatio Hornblower, forward to be examined for promotion to lieutenant.
Pellew cautions Hornblower to study diligently, because failure will mean an end to his acting lieutenant's grade and return to the midshipmen's ranks.
Mr. Tapling from the diplomatic service arrives, and he and Hornblower head ashore in Oran (part of Ottoman Algeria) to buy grain and cattle for the fleet.
When Caroline encounters HMS Dreadnought, Captain Foster sends a boarding party to take a few sides of beef, despite Hornblower warning him the quarantine has not expired.
At the end of the quarantine, no one appears ill, so they rejoin the fleet, where Hornblower receives a tongue in cheek rebuke from Pellew for the "wanton extravagance" of allowing his men to eat fresh beef.
At Gibraltar, Hornblower attempts his exam, a viva voce conducted by a group of senior officers including Foster.
Because of his heroism, Hornblower is not demoted to midshipman but keeps his acting lieutenant's rank and receives permission to take the exam again at a future date.