http://www.wsws.org/en/articles/2017/08/31/smi1-a31.html

Finland had formed part of the Russian Empire since the early 19th century. In the early 20th century, it became a preferred hiding place for Russian revolutionaries persecuted in the empire. In 1917, it was one of the most significant strongholds of Bolshevik influence. One major reason for this was the principled defense by the Bolsheviks of the right to national self-determination.

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Otto Wille Kuusinen, the principal figure in the Finnish revolution, later acknowledged:

The weakness of the bourgeoisie led us into being captivated by the spell of democracy, and we decided to advance towards socialism through parliamentary action and the democratization of the representative system. [8]

But the bourgeoisie had no intention of granting a parliamentary and peaceful transition to socialism. It immediately launched a counterrevolutionary offensive, relying primarily on German troops. Despite the significant growth of the Red Guards and the Baltic fleet, where Smilga, Dybenko and Antonov-Ovseenko had worked, the working class and the fledgling armed forces of the Bolsheviks were unprepared to fight against the Whites and the invading German and Swedish troops.

Within weeks, thousands and thousands of revolutionary workers were slaughtered. Victor Serge estimated that, in total, over 100,000 Finnish workers—i.e., a quarter of the country’s proletariat—were massacred. Some 70,000 Red prisoners were placed in concentration camps. About 50,000 of them were supposed to be shipped to Germany as slave laborers, a plan prevented only by the outbreak of revolution in Germany itself. The Bolsheviks had to give up hopes for the incorporation of Finland into a union of Soviet socialist republics, and the revolution in Finland was thrown back for decades.

This experience proved critical for the further conduct of the civil war by the Red Army. As Victor Serge later pointed out:

The total extermination of all the advanced and conscious elements of the proletariat is, in short, the rational objective of the White terror. In this sense, a vanquished revolution—regardless of its tendency—will always cost the proletariat far more than a victorious revolution, nomatter what sacrifices and rigor the latter may demand. One more observation. The butcheries in Finland took place in April 1918. Up to this moment the Russian Revolution had displayed great leniency towards its enemies. It had not used terror. We have noted a few bloody episodes in the civil war in the south, but these were exceptional. The victorious bourgeoisie of a small nation that ranks among the most enlightened societies in Europe was the first to remind the Russian proletariat that woe to the vanquished! is the first law of social war. [9]

From Wiki:

https://en.wikipedia.org/wiki/Georgi_Plekhanov#Death_and_legacy

Plekhanov left Russia again after the October Revolution due to his hostility to the Bolsheviks. He died of tuberculosis in Terijoki, Finland (now a suburb of St. Petersburg, Russia called Zelenogorsk) on 30 May 1918.

Google Maps, Zelenogorsk: