Let's start with the noticeboard near the beauclair marketplace for this particular quest, or if you prefer exploring you can find it naturally west of the tourney grounds. The cave entrance is pretty straightforward to spot but watch out for kikimores, they'll telegraph their poison attacks with a brief glow so dodge immediately when you see that flash. Once inside make your way through the thermal springs area the hot water sections require careful timing since you'll take damage if you stay submerged too long, maybe interesting to note that quen helps here.

The still filter piece is underwater in one of the deeper pools, and you'll want to look for blood trails and letters around the area that explain what happened with victor monnart and his three sons. When you reach the brothers' standoff, position yourself between them for better dialogue options, though if things go south be ready to dodge sideways since they tend to attack in patterns. Going for the peaceful route takes more patience but unlocks hugo monnart as a merchant at the clever clogs tavern which is pretty valuable. Combat wise, the brothers have predictable attack patterns they'll usually start with a heavy overhead swing giving you about a second to roll right before following up with faster strikes.

Good to know: key thing to remember is watching their stance changes, especially hugo who has this tell where he shifts weight to his back foot before his sweep attack. The whole thing flows better if you take your time with the dialogue choices and keep an eye on everyone's positions during the confrontation.