When Danny is captured by the GIW and his alter ego is revealed, the GIW discover that the reason Danny survived the portal accident and became a half ghost (instead of outright dying) was because of an anomaly in his DNA. When they attempt to replicate the accident on the other Fentons, it's revealed that Danny and his family aren't blood related. The GIW's new objective is to find Danny's remaining biological family. It's a good thing Danny's biological brother isn't just any ordinary kid. (Disclaimer - Includes graphic depictions of violence and major character death)