For staff: the Monday drop, two minutes to set up.

Before the children arrive. Take one thing down from its usual place, like a hook, a cup or a sign, and leave the spot empty. Make three small chalk dots on the floor leading under a bench or table. Put the printed strip at the end of the dots.

The sealed printable. Print the strip: DVN WKH FRRN. Print the paper wheel on the back: two rings of the alphabet, the inner one cut out so it can turn.

The episode. Read the story aloud, or play the recording. About five minutes.

Jobs by age. The youngest follow the dots and find the strip. Six- to eight-year-olds turn the wheel back three to decode it. The oldest start the case board: two columns, what we saw in ink and what we think in pencil.

The answer. ASK THE COOK. A wrong answer costs nothing; try the wheel again.

No printer? Write the strip by hand. Draw the wheel as two rows of the alphabet, the second shifted three places.

The Elders' Clue (for home). Write this on the back of the printable: When you were at school, what told everyone it was time to go home? Only a grown-up can answer it. Next Monday, pin their answers to the case board in pencil, under "what grown-ups remember". Nothing has to come back; the room carries on either way.

For the ride home. Ask: why did Sketch draw the hook before anyone touched it?