Answer: Secret Code #197

The secret message says:

RAIN

The shift was 11.

The secret note decoded: RAIN
The note, decoded.

Letter by letter

Secret letterCLTY
Real letterRAIN

Decode it with Python

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

secret = "CLTY"
shift = 11
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:

RAIN

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.