You came so close. The job was going so well. You just never expected that the police would have a surveillance cat. That's what you get for trying to steal things in an age where people are strapping a GoPro to everything they can.
As soon as you heard the sirens, you and your partner split up, and ran in opposite directions. No sense in you both getting caught, right? However, all you managed to pick up in the mad dash of your getaway was your gear, and your accomplice was the one closest to the loot. Bummer.
After waiting at the pre-arranged safe point should the job have gone south, your worst fears are confirmed when your partner doesn't show. However, you're in luck. In this day-and-age of camera-equipped felines, your local police department has taken to allowing people emails rather than phone calls when they've been incarcerated. A few hours later, the following message showed up in your inbox:
One look at the email and you know that all is not lost, as your partner is trying to send you a message that's clearly not meant to be seen by the police. Hopefully before being caught, they managed to stash your ill-gotten gains somewhere away from prying eyes.
It's only a matter of time before the boffins at the station crack the code, can you figure out where your stuff is and retrieve it before they do?
The cipher was not pre-agreed between you and your partner. You are the mastermind of the operation, and could be expected to figure the cipher out, whereas your co-conspirator was selected for their brawn, rather than their brains. The cipher is not complex, and can be performed without the use of pen and paper.