Pay attention to what's written at the top and bottom of the note.

At the top: "How many of your kind will be joining us here soon, Calvin?"

At the bottom: "Ps-Check your mailbox"

Check the Evidence Collection Form from Part 2.

Read the Rabies Booster Shot Email carefully.

The Rabies Booster Shot Email mentions snakes being transferred to Riverside Zoo. Pay attention to the colors of the snakes.

This is a simple Caesar cipher with a single key. The key is the answer to the question at the top of the note ("How many of your kind will be joining us here soon, Calvin?")

This note tells Calvin to check his mailbox and asks "How many of your kind will be joining us here soon?"

A black rubber snake was found in Calvin's mailbox.

The Rabies Booster Shot Email says 3 black racer snakes are being transferred to Riverside Zoo soon. The answer to the question at the top of the note ("How many of your kind will be joining us here soon?") is 3.

This letter is encrypted with a Caesar cipher shift, which means every letter has been shifted by three spaces in the alphabet.

Decrypted, the letter reads:

Calvin -

I can’t believe you just

did that. I used to defend you

when people called you a snake.

My mistake.

Stop playing the hero. It was

one mistake, and a squirrel gate

isn’t a fatal safety risk. You just love selling people out.

You better hope I don’t get fired over this, because I

won’t go away quietly like

the other two.

-Jordan