The adventures of two girls from Zeeland in Zandvoort.

Mavis Keeves is the daughter of a man who is ruined and dies as a result of reckless speculation, encouraged by Sir Harry Winderbank.

In the prologue, a boat with some shipwrecked persons is drifting at sea. Among them is Baron van Waldheim, who, before he dies of exhaustion, entrusts his little son Alfred to the care of his butler Hendrik. The evil Jan van Oort persuades Hendrik to give him the Baron's papers. When they put the boy ashore, he wounds himself on a nail (leaving a scar that will later prove his identity). For years Van Oort manages to pass himself off as Baron van Waldheim; he is married and has a daughter and a son. One day Hendrik turns up demanding a job as butler, swearing that otherwise he will betray Van Oort's secret. Meanwhile, Alfred - now an adult known as Ulbo Garvema - has become a teacher. Unaware of who Van Oort really is, he accepts the position of tutor to Van Oort's children. He falls in love with the daughter, but Van Oort refuses to give his consent to their marriage. Ulbo and the girl elope.

Janus Rechtsom, nicknamed De Mottige (The Pock-Marked), is an honest seaman with a heart of gold that belongs to Lena Doorn, the girl next-door. His rival Frans van Klarenberghe comes up with one scheme after another to seduce Lena.