You will run into evidence that the grave robber was there too, and you may also find remains of Professor Moreau's diary. Along the way some panther statues will come to life and attack note that these are specters and not real beasts. Soon you will find spike traps, but you don't need to cross them unless you want some loot. You will find a portal there, so enter it, and you will appear in the ruins. (50 ) Go to the new location and dive underwater. Now open your inventory and use the Old map of Toussaint which will tell you where to go next.
The trail ends quickly with no way to continue the search. The grave you are looking for is just west from the fast travel point however, someone has robbed the grave, so investigate with your witcher senses to find footprints and follow them. Go to Orlémurs Cemetery near Lebioda's Gate. Important: If you tip the boy it will count as 'Proof of Generosity' for There Can Be Only One (so just pay it, you cheapskate). Now you will have the option to tip the boy with 5 or not.
It can be from Triss only if you romanced her, otherwise it's always from Yennefer, but it's different depending on whether you romanced her or not. Right after Blood Run ends you will very likely run into a boy who will deliver a letter for Geralt.
