Adventurer and adventurer Dmitry Bykov sets off on a risky expedition in search of treasure at the invitation of his new acquaintances - Michael Chernov and his girlfriend Jane. Michael tells the legend that during the reign of Hetman Sagaidachny, one of the Cossack seagulls, loaded with diamonds, reached the shores of America, where the jewels were hidden, which have not been found to this day. Chernov owns an old map on which the exact location of the diamonds is marked. The company chosen to search for the treasure is very dubious. However, Bykov, who fell in love with the beautiful Jane, agrees to take part in this adventure. Having reached their destination with difficulty, the expedition members finally throw off their masks. Who will get the Cossack diamonds? Does this treasure really exist?