Unlock: Finish the “Saving Oliver” story mission.
“The Social Club” is not a normal type of mission. It has no rewards, and it doesn’t count as a mission for purposes of the log screen in your Handbook, but it does shed some light on what Jason and his friends were doing before they decided to come to Rook Island.
After you return with Oliver to the cave under Dr. Earnhardt’s mansion, you can find a dish of Earnhardt’s red pills in the food cache by Daisy’s boat, with a sign that says “Eat Me” underneath them. Taking one of these pills triggers a flashback to when Jason and his friends were partying in Bangkok.
After you take the first pill, go up to the bar and order some drinks. Jason wakes up in the cave shortly thereafter, but you can take another pill to reenter the flashback.
Should you do so, explore the club in search of Riley and Keith. From the bar, go downstairs to the dance floor. If you’re facing the DJ, the restrooms are in the back right corner of the room, and that’s where you’ll find Riley. That uses up the pills for now.
Returning to the cave with Keith also replenishes the red pills. Take one and you’ll be returned to the club right in time to put your weight on it. After you’ve had a chance to dance for a bit, there’ll be a short fight on the dance floor. Block the first punch and retaliate by pushing the button prompts onscreen, and you’ll get rushed out of the club. At that point, someone will suggest you go skydiving at this place called Rook Island, and we all know how that turned out.