Captain Mullins, commanding HMS Vigilant, has been sent to the eastern Mediterranean to discover what Bonaparte's naval forces have been doing there. Finding French troops are being landed on some Aegean islands, Mullins does what he must to put a stop to their activities. Moorish pirates too, are found to be savaging the inhabitants of several of the islands. The frigate and her crew soundly defeat several of the pirate ships and their slaves are freed.