The Balkan War of 1877–1878 did not end with the Peace of San Stefano, which was offensive to Russia. The troops of the White General Skobelev enter Constantinople, in response, Britain sends its squadrons to the Bosphorus and the Baltic. Russian tower gunboats and mine boats - against the formidable battleships Royal Navy. Forts of Kronstadt and Sveaborg - against the guns of Armstrong and Whitworth. Fierce naval battles, the success of which is decided by ramming strikes, mines and... very large guns! And somewhere in foreign latitudes, Russian military clippers, like hounds let loose from their leashes, have already broken out onto trade routes - the ocean hunt has begun! Will Britain remain the Mistress of the Seas? And against the backdrop of these grandiose events is the story of a young midshipman, a graduate of the St. Petersburg Naval Corps, who received his first assignment to the Baltic monitor “Sagittarius”. He will take his main battle there.