Answer: Secret Code #99

The secret message says:

INK

The shift was 6.

The secret note decoded: INK
The note, decoded.

Letter by letter

Secret letterOQT
Real letterIKN

Decode it with Python

This program does the decoding for you. Change the secret and the shift to crack other messages!

secret = "OTQ"
shift = 6
message = ""

for letter in secret:
    if letter.isalpha():
        number = (ord(letter) - ord("A") - shift) % 26
        message = message + chr(number + ord("A"))
    else:
        message = message + letter

print(message)

When you run it, it prints:

INK

Did you know? Shift codes are very old. A Roman writer called Suetonius said that Julius Caesar wrote secret letters by shifting the alphabet by three. That’s why it’s often called the Caesar cipher.