The knights will take you to Toussaint where you'll be greeted by a knight being attacked by a giant. As is tradition, Geralt jumps into battle. The giant Golyat is powerful, but slow. It doesn't attack in rapid succession, but instead attacks with one powerful move at a time. Those attacks are fairly telegraphed and can be dodged with Geralt's roll. Using the Quen sign acts as a good buffer in case you mistime a roll.
After Golyat is defeated, Geralt gets the head as a trophy. The Golyat trophy grants a 5 percent experience bonus from monsters. Nice! The knight who was originally trying to kill the Golyat will tell you that the main beast has struck again. From there, you'll follow Minton to inspect the crime scene.
When you reach the point, everyone will be gone. Geralt has to rely on his witcher sense to look for clues. Tracks can be found to the left of the dock where you arrive. Once found, follow them along the shoreline. You'll run into some scurvers. Just be sure to step away once they're almost dead since the explode to cause damage.
Make your way into the water to inspect some nets using your witcher sense. Geralt will want to inspect more nets that are in deeper water. Dive to the bottom and inspect them. You'll find a monogrammed handkerchief that reads "D.L.C." It doesn't stand for downloadable content. Report back to Miton with your findings.
Milton will want to question the locals at the nearby pub. Follow him to the pub. A fisherman found the body under a blood red sky that morning. The body was caught in his nets. He'll go on about how the beast is a messenger from the gods to punish the nobles of the land, but he'll also tell you the whereabouts of the body. It's in Corvo Bianco, which is your next destination.
Corvo Bianco is a nearby vineyard. You'll arrive just in time to see that a bunch of men have been slaughtered. Make your way down the cellar to find The Bruxa of Corvo Bianco.
Bruxa is a vampire battle that will require patience. She's vulnerable against Yrden Signs, Black Blood Potions, Vampire Oil and Moon Dust. Bruxa will often be invisible. When in this state, she can't be attacked, but can attack you. Mash the dodge button to avoid her attacks. When she takes human form, that's your window to attack. Be patient until you find an opening. The cellar is dark, so using a cat potion will help you keep track of her location.
So the Bruxa is defeated. Case closed. OK, not really. The Bruxa isn't the beast you're looking for. Inspect the body on the table to learn more about the beast in Geralt's contract.
Follow the path above Corvo Bianco to the tourney grounds. You'll speak to Baron Palermin. Geralt needs to meet with the Duchess to learn more about the attacks.
Palermin is just outside the tourney grounds. Geralt notices a Shaelmaar beast in a cage that is ready to go into the arena for battle. That battle gets out of hand, and Geralt has to intervene. The Shaelmaar is covered in rocks and is vulnerable to attacks when its belly is exposed. It's vulnerable against Aard Signs, Relict Oil and Samum bombs. Watch out for the beast's ground pound and roll attack. Wait until it rolls into the wall, which stuns it. That's the best time to strike with heavy attacks.
Once you've defeated the Shaelmaar, you'll have the option to kill it or spare it. Then the duchess will enter the arena to speak with you. You'll have a lengthy conversation with her and Damien De La Tour, the captain of the Ducal Guard. There you will learn more about the attacks and the beast for the contract. Milton is the next target, but he's in disguise for the town event.
In order to find him, you and the duchess have to split up to find three objects. Geralt is tasked with finding the golden fish and a unicorn. Head down to the water and use witcher sense to find the golden fish. It will be nabbed before you can grab it, which will trigger a cutscene. Eventually, Geralt smashed the fish and gets the Key from the Golden Fish. Next, head to the northeast to catch the unicorn.
Geralt will spook the unicorn (horse with a horn tied to its head), and will need to find something to lure it. Use witcher sense to find the ripe apple. Equip the apple and approach the unicorn once more. Once you grab the message on the horn, meet up with the duchess. The two clues Geralt found along with the duchess' clue tell you Milton's location. The answer to the riddle is "a greenhouse," but even if you choose incorrectly, the duchess will put you on the right track.
You'll arrive at the greenhouse too late for Milton, but just in time to find the famed beast that is responsible for the killings. A chase scene will put you in battle with the beast. It's a difficult battle. Actually, it's an impossible one. Geralt's death will trigger a new cutscene explaining who the new beast is, along with an introduction of an old friend.
Thus begins your hunt for Dettlaff Van Der Eretein.