The Last Bodyguard
Speak to a Green affiliated merchant by the southern docks in Alexandria to kick this one off.
He needs you to deliver precious cargo, but he's actually talking about his daughter- beautiful as she is willful, infuriating as she is irresistible, etc, etc. Start by grabbing a boat (she'll follow you automatically, with a certain ludonarrative dissonance).
Follow your marker to the Egyptians docks, then, through much pre-scripted dialogue, reclaim her horse.
Mount it and set off. The two of you will seem to dicker about your next destination, but your objective marker doesn't waver.
At the market, Kara will ask you to carry some linens for her. Ready a Predator Bow and be prepared to drop the bundle immediately, because as soon as you pick it up, her horse will be stolen by a bandit. If you're quick you can shoot him off the horse almost immediately, but odds are you'll have to tangle with whatever guards are nearby too.
When the killing's done, mount Pegasus and ride him back to Kara, then dismount and speak to Kara's father.
This completes the mission, granting XP and a hefty sum of drachmas for your troubles.