Blood on the Ice

Background
This is a multi-step quest which begins in Windhelm. It entails discovering the identity of a serial killer that has killed at least three young women by the time Windhelm is entered by the Dragonborn.

The body of the latest victim is in the cemetery, and the quest is activated when the nearby Windhelm guard is queried. There are alternative paths through the quest, so following the quest markers exactly may not be optimum.

There isn't really any forensic reasoning involved; common sense will suffice for the initial portion. The warning about alternate routes through the quest should alert the Dragonborn to question some early conclusions the various dialogue options seem to force.

The biggest "reward" from this quest is related to the Strange Amulet. After going through all the hassle, make sure not to bypass that section if desirous of having its full potential unlocked.

Initiating the quest
To initiate this quest, the Dragonborn must travel to Windhelm at around midnight. If the Dark Brotherhood quest-line has been started or completed, it could hinder the possibilities of starting this quest. If this happens and the murder scene doesn't appear, killing Grelod the Kind may fix this issue. At this point, this quest can be completed in one of two ways:
 * 1) In the graveyard, there will be several people gathered around the body of Susanna the Wicked . The guard will approach the Dragonborn and start a conversation that leads to the initiation of the quest. To get to the graveyard, turn left at the entrance to the city, go through the archway, make the first right and go down the steps behind the blacksmith.
 * 2) Buying the house Hjerim in Windhelm will also start this quest. In this case continue at step 8.
 * 3) Another way to start the quest is to steal the key to Hjerim from Tova Shatter-Shield and enter the house. When one of the fliers located on a small dresser is taken, the quest will start at step 9.
 * 4) After questioning the three nearby witnesses, the Dragonborn should talk to the guard again.
 * 5) In order to be granted permission to help the investigation, the Dragonborn must visit Jorleif, and then return to the guard.
 * 6) Inside the Hall of the Dead, the Dragonborn should speak with Helgird.
 * 7) If the key to Hjerim (purchased or pickpocketed) is in the Dragonborn's possession, the house can be entered to skip to step 9; otherwise, following the trail of blood in the crime scene will lead to Hjerim.
 * 8) Advice should be sought by speaking to Jorleif.
 * 9) Entering the house can be done by picking the lock or receiving a key from Tova Shatter-Shield, Friga Shatter-Shield's mother.
 * 10) All of the furniture that can be investigated should be.
 * 11) The Butcher's Journal #1 from the bloody chest up against the wall on the left of the entrance should be taken. The wardrobe on the right in the northwest room of the house will have a hidden door leading to an altar.
 * 12) The Butcher Journal #2 is at the altar.
 * 13) The Strange Amulet and pamphlets from the small dresser just next to the secret door should also be acquired. The amulet is hidden under the pamphlets.
 * 14) Jorleif will provide the investigator with information, suggesting to talk to Calixto Corrium (once the amulet is in hand) and Viola Giordano.
 * 15) The Strange Amulet can be shown, and eventually sold, to Calixto Corrium. He will inform the Dragonborn that it belongs to the court mage. The amulet is needed in order to accuse the court wizard, although it is recommended to sell it as it may remain in the inventory indefinitely after the quest is completed.
 * 16) Viola Giordano is often found in Candlehearth Hall. She can't be talked to unless a copy of the Beware the Butcher pamphlet is in hand. If the journal has been picked up before talking to her in the house, it can be dropped and picked back up in front of her to continue the accusation quest line.

Accusing the mage

 * 1) Returning to Jorleif will end the quest, accusing the court mage of the murders.
 * 2) Waiting three days outside of Windhelm will make a body appear outside Candlehearth Hall, reopening the case and start the second part the quest, "Catch the Killer". If the Dragonborn is maximum level waiting, three days will not work, instead, they will have to visit the court mage in the barracks jail (see bugs).

Catching the killer

 * 1) Rather than going to Jorleif, the Dragonborn can choose to talk to Wuunferth the Unliving, the court mage, directly. Accusing him of practicing necromancy will cause him to deny the accusation, telling the Dragonborn that the amulet and journals are not his. He will then direct them to where the killer will strike next.
 * 2) As soon as the marketplace area is visited (right by the White Phial; the quest indicator will be a little misleading) in the stone quarter after dark, although it is possible to complete the quest if visited during the day, Calixto will be seen about to murder a random female NPC (possible victims include Arivanya (if Wuunferth wasn't accused), Nilsine Shatter-Shield, Hermir Strong-Heart and if the Dragonborn has married a woman in Windhelm, her). He can be stopped.
 * 3) Alternatively, instead of stopping Calixto in the marketplace, if he is witnessed successfully carrying out this murder, he will run off into the night. The quest tracker will then lead back to Hjerim, where the killer lies in wait and will attack immediately upon entering. If the Dragonborn is fast enough, they can catch up to Calixto and strike him down, with no added bounty.
 * 4) Returning to Jorleif and telling him that the killer has been caught completes the quest.

If the amulet has been sold to Calixto earlier, it can be looted back after killing him. It turns out to be the fabled Necromancer's Amulet. It grants +50 Magicka, Fortify Conjuration 25%, and reduces Health and Stamina regeneration by 75%.

Trivia

 * If the Dragonborn is part of the Dark Brotherhood, and completes the quest Mourning Never Comes, killing Nilsine, Tova will be dead on the floor next to a suicide note in her house. Instead of talking to her, the key to Hjerim can be taken from her body.
 * After killing Calixto and obtaining the key from his body, the Dragonborn can go into Calixto's house. Another Butcher's Journal is in a chest upstairs. It tells the reason for all the killing.
 * Pickpocketing the key from Calixto while he is alive and stealing his journal is not enough to get him arrested.
 * When visiting Calixto Corrium (quest step 11), it is possible to sell him the Necromancer Amulet and then pickpocket the amulet in order to then sell it back. Each successful attempt is rewarded with 500 gold and a high Pickpocket experience (no Pickpocket perks are required). Once Calixto's shop is left, it will remain open for the rest of that day, but will lock and stay locked (Master) from then on. He will not be in there ever again. This only works for one day.
 * If the Dragonborn approaches the Windhelm Guard with a weapon drawn, the Guard will suspect them of being the killer. However, proclaiming innocence will be enough to convince them.
 * This quest may be a reference to the Victorian murderer Jack the Ripper.
 * If the corpse is turned into a pile of ashes at the start (using a Raise the Dead Spell), it will "reassemble" back into the regular body when Helgrid takes it into the Hall of the Dead.
 * If Hearthfire has been installed, Calixto may try and kill Sofie. However, since Sofie is a child, she won't die.
 * If a dragon attacks the city before the Dragonborn starts this quest and kills too many guards, there's a chance that the quest cannot be "started" even though there is a murdered body in the cemetery.

Bugs
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Fixed Bugs

 * Patch 1.5 resolved the bug where Calixto did not die properly on some occasions.
 * Patch 1.5 fixed the issue where if Viola Giordano is killed before purchasing Hjerim, the quest will start but be impossible to complete, and no upgrades will be purchasable for the house.

Unpatched Bugs

 * Killing any of the Windhelm guards may cause the quest to never start.
 * Sometimes, after accusing Wuunferth, the body will not appear outside Candlehearth Hall. This can be remedied by talking to Wunnferth (who can be found in jail via the barracks). Trigger the next part of the quest by choosing "the killer has struck again".
 * Sometimes after completion of the quest, even if Calixo is caught and Arivanye is saved, she may randomly turn up dead at the stables or around Windhelm.
 * Sometimes after investigating Hjerim, Calixto is untraceable, making it impossible to sell him the amulet. Talking to Viola Giordano still completes the quest.
 * If the Dragonborn proceeds with the quest by showing the evidence to Viola and speaks to Wuunferth without speaking to Calixto about the amulet, the option to say to Wuunferth "I guess Calixto was wrong" will still appear, and the Dragonborn will speak of the amulet as through they no longer have it. The quest will still proceed and be possible to complete, but after speaking to Wuunferth, Calixto's house will be locked and he will not be there, making it impossible to sell him the Strange Amulet and thus the Necromancer Amulet cannot be obtained.
 * On some occasions when Calixto runs to Hjerim, after being caught, the marker on the map says that he is outside the city walls, although he is not. If the local map is followed, it indicates his true location (Hjerim).
 * During the second half of the quest, the quest objective to search for the killer in the Grey Quarter at night may be given then immediately completed. Upon leaving the building Calixto will be seen running through the city and if any attempts are made to stop him in any way, he will call for help and the Windlhelm Guards will come to his defense. If allowed to escape, Calixto will eventually make his way to Hjerim where he will be hiding in the room hidden in the wardrobe, becoming immortal. He will not leave Hjerim and since he cannot be killed the quest will not end.
 * If Civil War Questline has been completed, the mission may not be able to be started as it is necessary to be able to talk to a Windhelm Guard and there are only Imperial Guards.
 * Entering Hjerim (after finishing Mourning Never Comes), reading the Butcher's Journal and Beware the Butcher as well as other things such as talking to the Priestess of Arkay and Nilsine's father and breaking into Calixto's house, taking the third journal-none of it has worked. It is also impossible to buy Hjerim as Jorleif (who is still the only one selling Hjerim) says, "There is a house available but there was some... unpleasantness.", however this does not start the quest. Nor does talking to Viola.
 * Sometimes,the previous map markers will not go away when proceeding to the next objective,causing them to all stay marked at once,even if all of the marked locations have been visited properly.
 * After chasing Calixto into Hjerim he can't be killed and becomes hostile when the Dragonborn enters.
 * After starting the quest, the quest journal permanently states "Get Assistance from Jorleif", rendering the quest unable to be finished, as Joleif will also bug, so no assistance can be gotten from him.
 * A possible fix for this is to pick up a butcher flyer and show it to Jorleif, who will then direct the Dragonborn to Viola. As long as they picked up the amulet and showed it to Calixto, they should be able to question Viola about the flyer and then accuse Wuunferth.
 * If the clues at Hjerim are investigated before Friga Shatter-Shield brings the Dragonborn to the house, the clues may not be findable again and there will be no dialogue allowing continuation.
 * Sometimes, going to the marketplace shortly after the conclusion of the quest may cause nearby townsfolk to become hostile for no apparent reason (no bounty added). A way to avoid this is to leave Windhelm and return a few days later.
 * If the magician is accused before speaking to Calixto it will complete the first part of the quest, however the amulet can not be removed from inventory. The new quest says to capture the butcher, however, he is immortal and the quest will not end.
 * Susanna the Wicked may never leave the Candlehearth hall, and therefore will never be killed. Commands cannot be used to force start quest.
 * The door to Calixto's House of Curiosities may remain permanently locked. If Calixto's key is stolen and the Butcher's journal taken from the locked chest above the entrance, Calixto may disappear entirely. Finding said journal does not start the quest nor does killing Susanna or Calixto himself.
 * If the Dragonborn accumulated a bounty during the first part of the investigation and bribed the Windhelm Guards, they cannot be interacted with afterwards and will only respond with "Wait, I know you". This will cause the second part of the investigation unable to start.
 * Fix: Commit a crime. This will cause the guards to apprehend the Dragonborn. After the Dragonborn has paid the fine or served their sentence the guards will now be able to be interacted with.
 * The quest will start, but no journal entries will show up, only the title will.
 * Sometimes as Calixto goes to the Stone Quarter for the final murder, he and the other character may get stuck and just stand in the Quarter indefinitely. Calixto cannot be spoken to during this time as it says he's busy. The only way to finish the quest is through console use, but the characters will remain stuck there and Wuunferth will also remain stuck in the jails despite being exonerated.
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