Note the bold letters in Hal’s note. When you pull them out, you get: 

Mx mw hsri. Wliw alivi rsxlmrk jpsaw sv kvsaw.

The butcher’s logo has a hidden number -4. Shifting the letters from the note - 4 letters, the following hidden message is revealed: 

It is done. Shes where nothing flows or grows.

This pertains to where her body is hidden.

Determining the correct order of Mary Alice’s errands that morning gives you the following order:

1. She left her home and walked to the docks, avoiding the most direct route which was unfortunately under construction. 
2. From the docks she walked to the party store and picked up her order. This morning timing is confirmed by her receipt and use of her credit card. 
3. From the party supplies store, she stopped by the bakery. 
4. Still a little sleepy, she then got a cup of coffee at the coffee shop by crossing the longest bridge, before stopping by Hal’s butcher shop just to say hi. She notes Tim is picking up the pig later, this is simply a social visit.  
5. On her way out of Hal’s, she chats with a friend by the Shane’s house - noted as the Victim’s house on the map. 
6. The margin note then says she realized she dropped her phone and went half way back across the long bridge to grab it. She turns around, not crossing all the way. 
7. She then goes to the dog park, and then the groomers.
8. Her final stop was the nearest bus stop. Her arms were too full to walk back home and she didn’t want the dog to get dirty again before the party. 

The stop signs on the map denote where one number ends and another begins.

Starting with the 6683 code from Mary Alice’s walking path, use the letter combination on the victim’s notebook (1st - 3rd - 3rd - 2nd) (meaning the 1st, 3rd, 3rd, and 2nd letter on each of those number keys), the code spells M-O-V-E

The graffiti and lipstick tube on the phone booth hints at the killer as well.

Hal’s note reveals the following hidden message: “It is done. Shes where nothing flows or grows.”

This is regarding where Patricia is buried. This eliminates the forest (grows) and the river (flows) as possible burial sites. This leaves the Garbage Dump or the Construction Site (see map). 

The flyer in Eric’s locker is for a party at the construction site the day of his party. This would create witnesses and commotion, eliminating it as a burial site as well. 

This leaves the Garbage Dump as the only viable burial option.

JENNY STILTON, ERIC’S AUNT, IS THE MURDERER. SHE WAS ASSISTED BY HAL, THE BUTCHER. 

1. She did it so Eric would stay closer to home for college. Him leaving was breaking her sister Mary Alice’s heart, who she loves dearly.
2. Hal was willing to be an accomplice for two reasons: 1) A handsome sum of money as noted on the receipt, and 2) he still had feelings for Mary Alice. 

Why Jenny did it:

• Patricia was dating Eric when he applied to colleges. They planned to go out of state together. Even after they broke up, Eric was still planning on going away to school, and remained close with Patricia. Jenny saw this hurting Mary Alice and wanted to keep him close to home. She thought that Eric wouldn’t go across the country without knowing anyone, so she felt she needed to get rid of Patricia. 

How she did it:

Jenny left Mary Alice’s house the night before the party after helping her set up. She said she was going to pick up the cake in the morning and be back the next day. 

• We know the cake was picked up later than originally planned, leaving Jenny’s morning open and unaccounted for.

Jenny instead drove to a pay phone near the butcher shop and called Patricia. She said that Eric still loved her and is hoping that she comes to his party tomorrow. 

Patricia is hesitant, but agrees. We know this because she called Eric afterward to confirm and Eric admitted to speaking with her in his statement. 

Jenny asked her for a favor since she lived so close to the butcher shop. She asked if Patricia wouldn’t mind helping her pick up the pig for tomorrow’s event. It’s too big for her to carry alone. Patricia didn’t mind and agreed to meet her at noon the next day. 

We know Jenny was murdered at the butcher shop from Hal’s note, and that he buried the body. 

• They killed her in the butcher shop  and put the head inside the pig. Jenny wanted to sear the image into Eric’s mind, reinforcing the need to stay home, close to family. 
• Even though  Mary Alice was out and about that day, she was at Hal’s much earlier than the estimated time of death. 

Where the body was discarded: THE GARBAGE DUMP

• The clue from the butcher’s note eliminates the river and the woods, leaving just the construction site or garbage dump as viable options. 
• The flier found in ERIC’s locker showcases a party at the construction site the same day that Patricia died. It’d be too busy to discard a body discreetly. 

Why it couldn’t have been: 

• Uncle Tim: He had no motive, and picked up the pig on time, 3 hours after Patricia was murdered. The lipstick tube on the payphone also signifies that the killer was female. 
• Mary Alice: Her receipts and confirmed errand runs that morning give her a solid alibi. Looking at the receipts she collected along the way, she was at the dog groomer at 12 P.M., Patricia’s estimated time of death.
• Caty, Eric, or Darren: All 3 were verified to be together the morning of the party. Their stories lined up.