This section of Assassin's Creed: Odyssey walkthrough includes the description of all side quests available in Korinthia. Each description covers the location, walkthrough, and the list of rewards.
Handle of Care
The mission starts: when you talk to Alikibiade after you complete the main quest.
Description: Upon starting this quest go to the location shown in the screenshot above - Akrokorinth Fort.
That is where you will be attacked by the opponents. Kill them all to get inside the building. There, you will meet a man - give him the package. After doing so, return to Alikibiade to finish the quest.
As a reward for completing this mission, you get the Alikibiade's Axe and approximately 200 coins.