The Goodies find a man about to commit suicide by jumping off a bridge and talk him out of doing so. It turns out that the man is the zookeeper in charge of in the brand new Monster House at the London Zoo and that he is depressed because he does not have a monster exhibit to put into it. The zookeeper mentions that he used to be the keeper in charge of the Snowdon Aviary at the zoo.
Tim, Bill and Graeme decide to go to Scotland, where they hope to be able to catch the Loch Ness Monster for the zookeeper to put into the Monster House.
