Season 1

The young siblings Tuuli and Joonas are sent away to spend their summer vacation at their grandmother's countryside house. Expecting a rather boring and uneventful summer, the vacation takes an unexpected turn. While exploring the area, the children decide to build a secret hideout near the edge of the mysterious "Rajametsä" forest, unaware of the deep secrets and adventures that lie ahead in the woods.

Tuuli and Joonas venture into the Border Forest, but they do not find the old cabin they are looking for.

A deep clean at Grandma’s place does not end well.

Despite the prohibitions, Tuuli and Joonas decide to build a den in the Border Forest.

Grandma’s neighbor, Seppälä, intends to cut firewood for himself in Rajametsä.

Tuuli and Joonas find a golden key at their grandmother’s house and end up solving the mystery of the Border Forest.