Three brave and skilled brothers bought a decommissioned real ocean rescue lifeboat, equipped it with a motor, dressed it with sails, built a cabin, and embarked on the most fascinating life in one of the largest ports in Europe – Antwerp. Mark – the youngest brother, 13 years old, the most restless; Bob – the middle one, 15 years old, but already an excellent mechanic specialist; Jan – the oldest and most prudent, 17 years old.
The book consists of three parts, in each of which this brave and audacious trio exposes international fraudsters and local gangsters.
In the first part, which gave the title to the entire book, the boys investigate the mystery of the old steamer "Altamare". The steamer is sent to the "graveyard" of ships, but immediately suspicious characters begin to hover around it.
In the second part ("Diver"), the boys help the police commissioner find those who are stealing cargo.
In the third part ("The Big Races"), the brothers decide to participate in sailing races, but even here they find adventures: risking their lives, they uncover a gang that steals cars. The races themselves are one of the best parts of the book with romantic panoramas, searches for the right tactics, and fierce competitiveness.
The heroes are very lucky: they have understanding parents who are not prone to prohibitions, encouraging independence and feeling all the impulses of the young soul. Moreover, they encounter other understanding adults, whether it's a port guard or a police commissioner. All of them speak to the brothers respectfully, as equals.