Sonic and Shadow have a secret. Every Halloween, that secret is in danger of being exposed but thanks to Tails, the only other person who knows, the truth remains hidden. This year however, Halloween is lit by a full moon. And now Knuckles is doing some digging where he shouldn't. The challenge to conceal and control is on and more difficult than ever.

After witnessing Sonic's dark super form whilst on a rescue mission, Sonic's friends want an explanation for the presence of the dark entity in their seemingly carefree hero. Meanwhile, Sonic's dreams are haunted by memories of his early childhood, before he met Tails and the gang. Are the two occurrences linked? Is the hedgehog's easy going attitude just a face?