Bertram was a peasant living in the village of Yantra on the east side of the lake, northeast of Novigrad. A bandit leader known as Little Red wanted to settle a score with him since Bertram sent witch hunters after her, causing her to lose half of her men in battle.
It turned out he had secretly made a prior deal with Little Red's group: he would point out who was worth robbing in the area and in return he got a share of the intake. Eventually he grew greedy and demanded a larger share but Little Red refused, so he sent the witch hunters after her group.