Fungus, and his wife Mildew, must disguise themselves as humans and journey 'Up Top' in order to try and persuade their rebellious son, Mould, to return home.
Eve helps the new family move into their home, but Fungus has other things to worry about - he has been spotted on a security camera.
Daryl makes a discovery when he sneaks into the house where Fungus and his family are living meaning the whole family must risk it all if they are to stay together.