Everyone has a Lifetime Deed Counter (LDC).

It works like this:

You offer to help with the housework: Lifetime Good Deeds +1
You steal your little brother's sweets: Lifetime Bad Deeds +1

Looks straightforward, huh? But what if your every thought was disputed by opposing forces of good and evil - by an angel wearing ray bans (called Windleberry) and a demon in the form of a wart (called Muddlespot)? And within your mind they were fighting a fierce battle over your actions, a battle dictated by a game of poker?

When Muddlespot is promoted from a devil's janitor to special agent, the pressure is on for him to infiltrate Sally Jones and make her Bad. If he doesn't, it will be Very Bad for him. But as his mission leads him down Sally's ear and into the deepest recesses of her mind, all becomes unclear. Just what does it mean to be good? And can it be good to be bad?