After having his spaceship wrecked by the dreaded finkumpoops, space pirate Captain Codswallop takes refuge on Earth and unwittingly brings three finkumpoops with him. The finkumpoops are small furry creatures called Fink, Um and Poop who as well as being technological geniuses are complete idiots. They have a habit of taking things apart and putting them back together again in such a way as to make them do things they were never meant to do. Because of the devastation they cause, planets known to be infested with finkumpoops are invariable blown to smithereens by a fleet of Gorbanian battlecruisers - a fate that awaits Earth unless something is done to rid it of finkumpoops. Robbie Callaghan is a schoolboy. The summer holiday has just begun and he is already bored. Forced to flee his house to escape the attention of a couple of doting spinsters, he stumbles upon Hobb's End, an old station that has been converted into a home-cum-workshop by a stage magician who goes by the name of Manfred the Magnificent.Mannie (as he is otherwise known) tells Robbie he has picked up a distress signal from somewhere out near Mars. Robbie, of course, doesn't believe him and tells him so.
That night, however, Robbie sees a strange light in the sky that leaves him wondering.In the morning, he gets a phone call from Mannie who claims a spaceship has landed in the scrapyard at the back of the old station. Still sceptical, Robbie rushes to Hobb's End only to be told the spaceship is invisible. Annoyed at being made a fool of, Robbie throws a stone in the direction of the alleged space ship and is astounded when it seems to bounce off something invisible.They are attacked by Captain Codswallop but saved by the invisible forcefield surrounding the spaceship. When the finkumpoops show up, the space pirate runs screaming back into the ship.
As Robbie and Mannie look on, the finkumpoops take a load of scrap from the scrapyard and turn it into an antigravity device which Manny gets his hands on. As soon as he turns on the gadget, he shoots up into the air.Robbie manages to communicate with the finkumpoops and persuades them to help him get Mannie safely back to earth. They turn a rusty old banger into a flying car and rescue Manny. During an encounter with Captain Codswallop, Toby - a friend of Robbie's - sees his trainers reduced to ashes by the space pirate's atomic ray gun. He is disheartened by his loss until the finkumpoops create for him the neatest-looking pair of sho