Enter rooms with a Tlingit warrior near their village until one of them kidnaps you.
You'll awaken inside the slave hut.
-> You get a whois: ...HAS BEEN ENSLAVED BY THE TLINGITS!
Also inside the slave hut should be Stenka, a kidnapped Russian. ASK STENKA ESCAPE.
SAY I PROMISE TO COME BACK WITH HELP.
Note: this appears to be broken as of 14/05/2020, right now you can only SIT BOX and escape losing the possibility of the other two whois options
-> You get a whois: ...HAS PLEDGED TO HELP FREE A TLINGIT SLAVE!
SIT BOX. You are dumped outside with the trash.
You get a whois: ...WAS ENSLAVED BY THE TLINGITS BUT MANAGED TO ESCAPE!
You get xp!
You gain Tlingit enmity.
To free Stenka, choose one course of action:
Find one of Stenka's friends in the Russian fort (Sonov, Teodor, maybe others just replace the name in the following).
ASK SONOV STENKA. He asks what happened to Stenka.
**TALK SONOV STENKA WAS ENSLAVED . Sonov asks if you'll help. SAY YES.
Sonov follows you. Go to the Tlingit village outside the slave hut. Sonov frees Stenka.
...HELPED FREE A COMRADE ENSLAVED BY THE TLINGITS.
You get more xp!
Find the Tlingit man without a name. Kill him and get his carved redcedar key.
Unlock the slave hut and enter. Stenka escapes. You should leave too.
You get xp!
You get a whois: ...CLEVERLY FOUND A WAY TO FREE A TLINGIT SLAVE!
NOTE: This quest needs revision, when I attempted the Sonov route he requested proof Stenka was alive, and I didn't have time to investigate
Update 2021/06/30 -- Sonov route appears to work again -- Ask Sonov "Stenka", Talk Sonov "Stenka was Enslaved", Talk Sonov "Yes" resulted in success.