Anonymous Message is a written note found in Dishonored.
Who we are is irrelevant right now. Just know that we have faith in you.
Here is the key to your cell. Once you're out, head for the prison's Interrogation Room. Take the explosive there and plant it on the outer door. When the bomb goes off, run. Make for the river and lose yourself in the sewers. You'll find some useful gear stashed there.
And good luck. We need you alive and well for what's to come.
- A friend.