Isaac helped unload some of the Lacrima from the boat's deck.
Isaac finished his portion of the hauling and sat for a rest.
Immediately he went to pull his mask up and realized it was not there, a grimace soon following this discovery
His mask had sentimental value, he didn't want to lose it. 
But to get it back would be hard. 
His face is known in Magnolia after the incident with the third guard getting away alive.
There would be a bounty for sure, but he could get in, get it and get out, right?
He quickly rushed to his room and grabbed his weapons.

Soon Isaac found himself sneaking through the back-alleys of Magnolia, trying to make it to the last place he saw his mask quickly and without being recognized.
His weapons were a dead giveaway with their unique curved tips, but they were so large he could not conceal them.
He was halfway there when he decided to take a break.
The mute man sat in a very short alley and took a rest.
Guards did not worry him too much, it was magic users in the city that did.
Phoenix Wing was the Brotherhood's main threat and by the looks of the ship and his Guildmates, they must've ran into someone powerful enough to contest.
He had to assume it was Phoenix Wing, them being the closest guild to object to the Ragged Brotherhood's raid on the island.
He sat for a while longer, he heard people chatting in the bar to his left and glass broke in a restaurant to his right, followed by angry shouts.
Isaac laughed, which was rare. It was rare to hear Isaac at all.
When his laughing subsided, he sat back against the far wall of the alley and watched the entrance of the alleyway intently as he rested.