Rescue Sinthia

Rescue Sinthia is a side quest in Fallout.

Quick walkthrough
If the Vault Dweller spends a night in the Crash House Hotel in Junktown, they will wake up to find the hooker Sinthia held hostage by a crazed raider in the room adjacent to theirs. Marcelles will beg the Vault Dweller to defuse the situation.

Detailed walkthrough
There are three ways to solve this quest:

Peaceful solution
As soon as the raider can see the Vault Dweller, he will enter dialogue. When talking with the raider, the Vault Dweller must assure him that no one is going to hurt him in order to have him believe that the Vault Dweller is a friend, and not an enemy. This dialogue progresses through numerous pauses. If the Vault Dweller's Speech skill is high enough, he/she can convince the raider to leave without a fight. If the check fails, they may need to pay either 100 or 200 caps, depending on what dialogue options are chosen. Saving midway through the dialogues and re-loading will reset the encounter (however, see note below).

Violent method
Another option is to just fight the crazed raider, be it conversation first or not. If he says he needs to think about it, the Vault Dweller should walk in on him while he is pondering. He will attack the Vault Dweller instead of Sinthia, allowing them to kill the bad guy and save the hooker.

Sneaky way
Again, like the option above, the Vault Dweller should talk to the raider in a calming manner. When the raider says he needs to think about it, the Vault Dweller should begin sneaking. If the Vault Dweller's Sneak is high enough, both the Vault Dweller and Sinthia will be able to sneak behind the raider without him reacting. Shooting him will knock him unconscious. At first, Sinthia will think the raider is dead, but the game confirms he is not.

Rewards

 * 1000 or 400 XP.
 * A free night at the Crash House.
 * Sinthia's "services".