The Melkersson family arrive on the island where they have rented a house for the summer, only to find out that it's not as wonderful and idyllic as they had pictured.

Teddy and Freddy take their new friends Niklas and Johan on a trip to one of the rocky islets in the outskirt of the archipelago. They also take Båtsman with them, which makes their little sister Tjorven angry, because it's her dog. When Tjorven's parents don't recognize her complaints, she decides to leave the family and become a housekeeper to Söderman. Johan moors the boat too loosely at the rocky islet and when the four young friends are eating fish by a fire, the boat drifts away. Their boat is saved by the girls teacher Björn, who happens to be in his boat in...

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.

On midsummer, Malin is courted by Christer but the children do their best to stop him.

In a book Melker finds the maxim "This day - a life". He decides to make the maxim come true this very day, but despite his good intentions, all his undertakings end in disaster. He builds a water-conduit to the kitchen, only to find out that the whole kitchen-floor is flooded with water. He cook fishes for the dinner, but the food is uneatable because of too much salt. Christer invites Malin to a boating excursion and is not happy when she brings along her little brother Pelle. In the end Christer leaves Saltkråkan with the intention of never coming back.

Söderman urges Nisse Grankvist to report to the police that some thieves are stealing fishing-nets from the fishermen. Johan, Niklas, Teddy and Freddy go on a boat-trip to Kattskär, an island far out in the outskirt of the archipelago, where they are going to stay overnight in a cottage. The island is uninhabited, but there are some cottages, which are used occasionally by fishermen. The four young friends think they are alone on the island. They don't know that the thieves, Berra and Elis, are using the island as their hiding-place.

In the morning Teddy, Freddy, Johan and Niklas discover that they are not alone on Kattskär. They quickly understand that the two strangers on the island are the thieves that steal fishing-nets. Johan sneaks on board the thieves' motor-boat and takes the sparking plugs, so the thieves cannot leave the island. The children throw the sparking plugs into the sea. The thieves try to lay hand on the children's boat, but the children succeed to go away in their boat, leaving the thieves on the island, where they have to stay until the coast guard captures them.

If there's something uncle Melker really likes - mushrooms. Another island, nearby Saltkråkan, has got the biggest and the best mushrooms. But even though the island is small, it's quite easy to get lost.

Today it's Tjorven and Pelle's turn to go and get some milk at the farmer's place. But the trip becomes a little bit longer than they've planned, and when they come back home again they've brought a new little citizen to Saltkråkan.

The family of Melkersson arrive to Saltkråkan for celebrating Christmas. The children can't wait for meeting Santa - who's actually living nearby.

Jansson's hen-house has been visited by an uninvited guest - a fox! Björn goes to the barn with his carbine, but this night there are more than just one visitor.

It is summer again and the Melkersson family have returned to the island. Their rented cottage, "Snickargården" is to be sold to a rich gentleman and his posh daughter and this may mean this is their last summer on the island.