The third part of Assassin's Creed Odyssey: Legacy of the First Blade starts in Achaia. The first mission, The Simple Life, starts when you reach Darius.
Darius is waiting for you in the village. Approach him to trigger a conversation.
Look for your son together with Darius.
Reach the beach and start an investigation. Examine the vases, the ship, and the tracks on the ground.
Go with Natakas and collect shellfish. Approach the traps to remove shellfish that were caught in them. Speak with the man and reach the cliff to end this mission.