My notes on the encounter were simple. Groups of street urchins were in league with the city guards. The street urchins would accuse the party of some horrible crime. The guards would arrest the party. Then the guards would offer to let the party go for a price.
The party ties up their ship at the docs and head off to find a contact in the city. They notice two street urchins watching them. They are young boys wearing dirty and ragged clothing. One boy runs off down a side street. The other boy continues to watch the party. The party continues walking down the docks.
One player character pulls out a gold piece and holds it up. Then the player character throws the gold piece off the dock into the water (reminiscent of a recent scene in Boardwalk Empire). The street urchin recovers the gold and returns it to the character. The character says the boy can keep the coin if it leaves them alone. The boy runs off.
The party continues down the docks. Seven street urchins run out of an ally and accost the part. One of the urchins tries to sneak something into the pocket of one of the party members. The urchin fails and is caught. As the character grapples the urchin, two more run up and smear blood on the character while a third whistles. Out from the ally runs a third urchin. The boy is naked and blood covers his mutilated gentiles. The blood covered urchin screams, "He's the one!" and points at the character covered with blood grappling a young boy.
At this point, the city guard arrives. My idea was to capture the party then shake them down for gold. Instead, the characters decided to resist arrest. In a short time all eight urchins and two guards lie dead. The party runs back to their ship and sails away.
I found the image on DeviantArt here: http://javertime.deviantart.com/art/but-they-have-bloody-hands-137547649
Here is the video of the adventure.