Season 1 of Seventeen premiered on December 3, 2017.

The year is 1917. Rumors of the Russian Revolution are spreading to Helsinki, disrupting the lives of both Prime Minister Oskari Tokoi and the bourgeois Nikolajeffie family. The family's 17-year-old daughter Olivia and the same-aged maid Iita, who works for the family, are best friends. They meet a young socialist boy, Juho, and become entangled in politics, which puts their friendship to the test. Olivia disappears, and Iita realizes that it is a matter of life and death. At the same time, Oskari Tokoi's government seeks to make Finland independent from Russian rule.