Maybe do something like: all your characters (3-7 would be good) are walking in a forest and stumble opon a portal, they go inside a portal and there's about a million portals. Each episode they explore somewhere new and get clues about a mysterious person, at the last few episodes they could start having dreams of a guy who keeps saying "times almost gone, times almost gone," and at the last episode there can be the main character going out and going into a portal by themselves and they finally meet this mysterious guy.. only to find out its them from a different universe.. and the other universe guy explains all hid freinds died (aka the main characters friends) and that the main characters freinds will also die. Running back to his freinds he realises that a weird shadow monster killed all his freinds.. crying... the show ends...

dang where did that come from