The fog is coming in from the sea at the outskirt of the archipelago. When Johan, Niklas, Teddy, Freddy and Båtsman leaves the rocky islet out there, they get lost with their boat in the fog. Back home on Saltkråkan people hear about the fog in the weather report. Melker is alarmed. Nisse tries to calm him down, by pointing out that the sea is anyhow dead calm. The four young friends and the dog finally arrive at an island. They rove about until they find out it's the island where the school is.