This achievement is Earned during Case 3 - Infamy
In the Green Dragon tavern, you are tasked with creating a distraction in order progress past the guard.
In the first room of the tavern you must peroform various eavesdropping tasks.
Follow the guy outside for a smoke and steal his wallet
Go behind the bar, upstairs and into the gambling room
Interact with the Window and Door.
Press RB to activate Detective mode near the table where people are playing cards.
Highlight both sleeves and the mirror on the knees
Press LB to activate the Imagination - You must create a sequence of events to create a distraction.
The Correct sequence
1. Distract the man on his own.
2. Take the Knife
3. Cut the Rope -
4. Start A Fight
5. Guard Moves Away.
Confirm the sequence, watch the cutscene and Watch the Cards fall where they may the achievement unlocks, following the cutscene.
Hope this helps