When you are in the fishing village you can flag this side-quest in which you talk to Aida's daughter Yasmina and you learn that Harun has been tossing people out of the village - and two kids have left to look for their mother who Harun ejected and are now missing.
Harun is sitting on a couch on the footing of the bridge - head out to that by swimming to have a chat with him and learn why he did what he did.
Next go talk to Yasmina who whines and complains. After all in a predatory environment you are going to have predators!
She describes the places that her brother and mother should be at - so all you need to do is find the house with the red flowers behind the tunnel first, and then make your way to the Red Flower Cafe.
Secure the house and you find Jamie in a cabinet. Jamie tells you where his Mum should be - the Tool Shop - so now you need to head there!
When you arrive and pound on the door you talk to him - he denies everything - tells you that the woman is dead, and then decides to sound his alarm to draw in infected to deal with you.
You are going to need to kill him once you deal with the infected. After he opens the door and you have killed him search the shop - in a cell in the basement you find the mother - you talk with the mom and explain what she needs to do.
That wraps up this side-quest!