Every entry of a Soviet submarine into combat service was a secret operation. But there were also such trips, the purpose of which the crews of the ships learned only at sea. The author of the book, the famous Russian writer-marinist Nikolai Cherkashin, who served on submarines of the Northern Fleet, talks about the most secret operations of the once most powerful submarine fleet in the world of the USSR. The book includes field diaries of submariners who participated in breaking the US naval blockade of the island of Cuba in 1962, as well as stories of participants in secret operations - commanders of strategic nuclear submarines, commanders of flotillas and fleets. The book opens another page in the chronicle of Russia's "hidden fleet", full of drama and courage of Soviet submarine sailors.