A Fine Night of Debauchery is a main story mission in Red Dead Redemption 2 given by Josiah Trelawny, as part of Chapter 4.
It's the 52° mission in chronological order of the RDR2 story mode, played with protagonist Arthur Morgan.
A Fine Night of Debauchery - Mission Details:
While at the Mayor's party, the gang learned of a card tournament being held on the Grand Korrigan riverboat. Strauss and Trelawny fix a game so Arthur can win big on the tables.
Mission Objectives
Gold Medal Objectives (100%)
The following are the Mission Objectives required to obtain the Gold Medal in the mission "A Fine Night of Debauchery":
- Win the game of Poker without Strauss’s help
- After your cover is blown, escape the boat in under 35 seconds
- Get 5 headshots
- Complete the mission without taking any health items
Note: You must complete all Gold Medal requirements in one single playthrough of the mission.
A Fine Night of Debauchery: Mission Info
- Mission Number 52
- Story Chapter Chapter 4
- Mission Giver
Josiah Trelawny - Mission Type Mandatory Mission
- Protagonist (Playable)
Arthur Morgan - Location The Grand Korrigan riverboat (Bayou Nwa, Lemoyne)
- Rewards Gang Share: $3,000.00; Arthur's Cut: $825.00
- Unlocked Items
Semi-Auto Shotgun - Featuring
Riverboat Semi-Auto Shotgun 
Javier Escuella 
Leopold Strauss