C´est bon j´ai réussi à répondre à ma question. Je laisse l´info pour les futurs joueurs qui demanderaient la même chose.
Source : GameFaQs
"Then save and enter the bar. Enter the door in the back that leads to the
wine cellar. Talk to the employee there and choose the third option.
BOSS: Captain Dolce + 1st Lieutenant + 2nd Lieutenant
[...]
REWARDS: Werewolf Choker
Equip the Werewolf Choker right away to someone who builds echoes quickly. It
is one of the best accessories in the game, because it doubles the rate a
character can build echoes.
If this is your first playthrough, you will also get a Peace Earring. If you
are on the second playthrough, you get Pirate´s Paper 3. Be sure to examine
the barrels nearby for Score Piece 20 before you leave, then exit Baroque
City to the south."