Overview
The Sad Tale of the Grossbart Brothers is a secondary quest in The Witcher 3: Wild Hunt, set in Blandare and at the Grotto on southeastern Ard Skellig, in the Skellige Isles.
Djenge Frett
By the Blandare signpost, a Skelliger named Djenge Frett proposes a partnership: together they take out the Grossbart brothers, Jesse, Hegel and Manfred, three outlaws with a long record of brutal crimes, and share the bounty. If Geralt has already killed them, Djenge is delighted, takes directions to the bodies and hands over half the bounty.
The grotto
Otherwise, Djenge turns up again inside the Grotto on the right-hand path and asks if Geralt has made up his mind. Only agreeing lets the quest succeed. If you team up, Djenge has to survive, and he is not good at it. Using Axii on him before he charges ahead lets you deal with the brothers yourself.
If Geralt refuses, Djenge goes in alone and will probably die. To save the quest in that case, let Djenge reach the brothers and start the fight, then jump in to rescue him. Attacking the brothers before he does can fail the quest even if he lives.