"The Thomson brothers - known Templar smugglers - are visiting the Cayman Islands to conclude a lucrative deal. Find them and put an end to their schemes."
Once you take the contract climb onto the rooftop above the coop and free run to the East. Get to the edge of the plaza and use Eagle Vision to identify both targets. With all the soldiers around them it is just easier and quicker to take out both targets using Berserk Darts and avoid the big fight that would result otherwise.