Ms. Vale needs a detective. Turn your sound on.

Lessons you need for this case

The six notes in this case use five secret codes. You must have finished all five code lessons to solve the whole mystery. If you skipped one, go back and learn it now.

Check the box next to each lesson you have finished.

    Check all five lessons to open the case.

    How this case works

    1. Read about the case and meet the eight suspects.
    2. Crack the six notes. Nobody will tell you which code is which, and one of the notes holds the secret word you need to read another one.
    3. Answer three questions. Who is the Backwards Burglar? Where were the treasures hidden all these years? Why are they being put back?

    Be careful with step 3. A wrong answer locks the answer box for 3 minutes. Guessing will not work. Cracking the notes will.

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    Teacher note

    Answers are inside. Enter the teacher password.

    What is going on

    Fifty years ago, five treasures were stolen from the Copper City Museum in one night. People called it the Great Museum Robbery. A man named Slick Eddie Marlow went to prison for it, but the treasures were never found.

    This week, they started coming back. On Monday morning the Copper Crown was sitting in its old glass case. On Tuesday, the Jade Frog. On Wednesday, the Golden Compass. On Thursday, the Moon Pearl. Only the Star Ruby is still missing.

    Nobody has ever heard of a burglar who puts things back. The museum director, Ms. Vale, has hired you to find out who it is.

    What we know

    The treasuresFour of the five are back, one each night. Experts checked them. They are the real ones.
    The doorsCameras watch every door. Nobody has come in or gone out at night. No lock was touched. No alarm rang.
    The notesEach treasure came with a note in secret code. Two more coded notes turned up in the building. All are in the same brown ink.
    The old caseSlick Eddie Marlow spent ten years in prison for the robbery. Until the day he died, he said, "I did not do it."
    A backpackEddie Marlow, the grandson of Slick Eddie, was seen outside the museum three nights this week with a big backpack.

    Ms. Vale says: "It is the Marlow boy. It runs in the family. I do not care that he is putting things back. Nobody sneaks around MY museum."

    The timeline

    • Fifty years ago. The Great Museum Robbery. Five treasures vanish in one night. That same night, the tall clock in the lobby stops at 2:15. It has never worked again.
    • Forty-nine years ago. Slick Eddie Marlow is sent to prison.
    • Monday. The Copper Crown is back in its case.
    • Tuesday. The Jade Frog is back.
    • Wednesday. The Golden Compass is back.
    • Thursday. The Moon Pearl is back. Ms. Vale hires you.
    • Saturday. The museum turns 100 years old. The whole city is coming to the party.
    A word to know: innocent. Innocent means you did not do the thing you were blamed for. Sometimes an innocent person gets blamed anyway.

    Eight names are on the list

    Each of them has a reason, or a way to get near the glass cases. An alibi is proof that you were somewhere else when it happened. Look at who has one.

    Ms. Vale says: "Why is my name on this list? And the mayor? Cross us off. Start with Eddie Marlow and his backpack."

    The six notes

    Every note has a secret message. First work out which code it is. Then crack it. The keys are in the Code toolkit tab. You need all six notes to answer who, where, and why. Each note was found on the day shown.

    Notes cracked: 0 of 6

    Atbash Cipher Review the lesson

    Atbash is the mirror alphabet. A swaps with Z. B swaps with Y. C swaps with X, and so on. Look up each code letter on the top row. The real letter is right under it. It works the same way in both directions.

    Pigpen Cipher Review the lesson

    Each letter is drawn as the shape of the pen around it. Shapes from the second grid and the second X have a dot. Use this key for this case.

    Polybius Square Review the lesson

    Every letter is two numbers. The first number is the row. The second number is the column. I and J share a box.

    Rail Fence Cipher Review the lesson

    The letters are not changed. They are written in a zigzag on the rails of a fence, then read one rail at a time. Here is HELLO WORLD on two rails.

    H . L . O . O . L . . E . L . W . R . D

    Read the top rail, then the bottom rail, and you get the code: HLOOL ELWRD. To crack one, count the letters and split them into a top rail and a bottom rail. If the count is odd, the top rail gets the extra letter. Then zigzag: top, bottom, top, bottom.

    Keyword Cipher Review the lesson

    Write the secret word first. Then write the rest of the alphabet after it, skipping any letter the word already used. That is the code alphabet. Type the secret word here and the strip builds itself. Look up each code letter on the top row. The real letter is right under it.

    No secret word yet? Count the letters.

    In English, E and T show up more than any other letters. A is next. The letters that show up most in a coded note are good guesses for E or T.