To Catch A Cannibal

To Catch A Cannibal was going to be a quest in Van Buren, the canceled Fallout 3 by Black Isle Studios.

Quick walkthrough
This quest becomes available once the Prisoner has joined Caesar's Legion. Speak to Terrence about the disappearances of the slaves in the encampment and he'll admit that animals and slaves have gone missing, and encourages you to speak to some of the legionary recruits to get to the bottom of the mystery.

Detailed walkthrough
Travel to the legionary recruit section of the encampment and ask around. Most of the recruits are too scared to admit anything, but if the player has a high enough Speech skill or uses intimidation, they'll fess up that they've noticed a shadowy figure leave the encampment in the late night with one of the slaves or animals.

Head to the slave pens on the east side and interrogate some of the slaves. You're not going to get much out of anyone, since they're too scared to admit anything either. Ask Nina, the slave girl in the third pen, regarding the disappearances. She'll confess that her mother has been missing for days, and she describes that a "mean-looking" legionary has been abducting slaves. Despite very little information, head back to Terrence. He suggests that Cruz matches Nina's description, and he tells you to investigate Cruz's tent for any evidence that may link to the disappearances. Track down Cruz's tent on the western side of the camp which isn't too far from Terrence's. Notice the blood trail that leads to Cruz's footlocker and pick the lock. Cruz has some nasty collectibles, like a war cheif's severed head and bones. What you're after is his bloodied journal, which reveals that he's been visiting a cave not too far east from the encampment.

Travel outside the Legion camp on the southwestern dirt path until you reach Beastcaller Cave tucked behind two jarring rocks. There'll be a nightStalker waiting for you at the entrance of the cave. When you enter, you'll notice this isn't a regular cave. The cave drawings on the wall and the ceremonial burials indicate this is a long forgotten tribal hall of the dead. Continue through the cave where there's a few radroaches and other beastly critters guarding the tombs. When you reach the great hall you'll find Cruz devouring on some poor slave. He's surprised that someone was brave enough to investigate his whereabouts, and he admits to his cannibalistic abductions. He claims to be a cannibal descendant of the Beastlords, and he challenges you to slay him in front of his ancestors. You can listen to his backstory of how the Legion captured his tribe and forced him to join, or you can just begin fighting him immediatley. Cruz is a tough opponent, with a leveled thermic lance to boot.

After defeating Cruz, make sure to loot the corpses and head back to Terrence. He's deeply troubled by the news, but not entirely surprised. He admits that the Legion has been telling Cruz lies that he was a descendant of the Beastlords in order to build him as a terrifying threat on the battlefield. Terrence never thought the lie would ever escalate until Cruz discovered the burial hall for the Beastlords. He rewards your efforts with 500 caps, and the Prisoner gains 10 points of repuation within the Legion.