Elysana's Second Quest
If you haven't got the picture yet, this babe is trouble with a capital T, and that rhymes with P, and that stands for "poisonous". At some point after completing her first quest, you'll receive a letter from her inviting you to come to Wayrest to take care of another little matter for her. The second little matter is escorting her cousin somewhere. This is very straightforward. Once you accept the quest, the cousin's face will appear on your screen. Go to the designated town, find the designated person and deliver the cousin. You might be surprised by who you get to deliver her to. I've delivered the cousin to Gortwog and Brisienna, which had all sorts of interesting quest implications since they jumped the gun and started me off on quests a little early. You are supposed to deliver the cousin to a random NPC in a random town. In any event, if you have not completed the Blades quest, you should start running into assassins fairly soon. One of them will have a piece of paper which will mark Lysandus' Tomb on your map.
The only reason to take this quest is if you don't know where Lysandus is actually buried or if you get your jollies out of being hounded by people who want to kill you. If you're sitting around with nothing to do, you might want to take it just for the occasional excitement of having random assassins pop up.