This episode tells of what happens before Sonic & co. leave for home. Everyone is sad that they'll leave, especially Chris. There are many flashbacks to the first two episodes until they leave. Eggman, Cream, Amy, and Knuckles leave, but at the last second, Chris shuts the portal to Sonic's world, leaving Sonic trapped on Earth. So begins the (not so) long journey of Chris and Sonic... (thetvdb.com)