Dixon Bainbridge asks Bob Fossil to set up a highly illegal and shady kangaroo boxing match between the terrifying 'Killeroo'… and Howard. Howard thinks that by winning the fight he will impress the Head of Reptiles, Mrs Gideon. Vince enlists his uncle, a bare-knuckle fighter with a very strange accent, to help with Howard's training.

All is not well at the Zoo-niverse. Animals are disappearing one by one. Things go from bad to worse when Joey Moose, one of the zookeepers, goes missing. When Mrs Gideon reports that her python is also on the missing list, reported stolen, Howard is determined to save the day. Howard and Vince stumble across Dixon Bainbridge’s secret laboratory and the terrible truth behind his ‘experiments’ comes to light.

Bollo, the eldest and most respected gorilla at the Zoo-niverse is gravely ill. Bob Fossil persuades Howard to dress in an ape suit, replacing Bollo, so that he can continue accepting sponsorship money for the gorilla. Everything’s going smoothly until the Grim Reaper arrives and mistakenly takes Howard off to Monkey Hell instead. Vince, guided by the ever-resourceful Naboo, sets off to rescue Howard, and on the way meets Mr. Susan, caretaker of the Mirror World. Howard and Vince run into trouble when they encounter the Ape of Death who is plagued with problem hair – but Vince knows hair and may have the perfect solution.

In an attempt to compete with daring adventurer, Dixon Bainbridge, Howard and Vince set off in search of the Egg of Mantumbi. Into the whiteness, the nothingness of the Arctic Tundra, the boys come face to face with hideous ice demon, Black Frost. Luckily, Vince has befriended a polar bear.

Dixon Bainbridge, owner of the Zoo-niverse, is intent on selling to the highest bidder. There's a road being built through it and 'if the animals won't work on it, they'll be underneath it'. Howard and Vince embark on an arduous trip deep into the Jungle Room, in search of the only man they think can help save the zoo - Howard's hero, Tommy Nookah.

Howard is hell bent on a career as a serious writer. He thinks it will also improve his chances with Mrs Gideon. When a famous publisher, Hamilton Cork, arrives at the Zoo-niverse, it's Vince's literary efforts, in the shape of Charlie, a pink bubble gum character, which takes Cork's fancy. Meanwhile Bob Fossil has embarked on a new breeding programme for the pandas.