Ergo lives somewhere between the olden days and last week, and is middle sized. He likes music and would love to play the piano, but is challenged in that ambition by the absence of hands, but, as he is quick to point out, he does have “knobbly bits”. He meets a Fairy called Elsie (known as “Little Else”) and when he is far away from her he thinks of Little Else. Elsie, unusually for a fairy, finds Ergo attractive, and Ergo feels the same about Elsie, but they are too shy to exchange this important information.

Hearing about the evil Pigfrogs that come out at Christmas to squash you just for fun, Ergo becomes incensed, and, aided by Nigel and Dotty Farnsbarnes (Elsie’s sister and brother-in-law, who own his and hers matching combat helicopters) he recruits a mighty army of slugs, trolls, humanoid creatures and travelling pixie accountants called gnome-adds. They fight the Pigfrogs by pretending it is Christmas when it isn’t, and tempting them from hibernation in order to do battle with them while the enemy is half asleep and confused. The military regime of General Moundrot (whose wife, Ursula also wants to play the piano) is made less efficient by the idiotic Captain Quirkhardt who after leading Third Battalion to its doom at the “hands” of the slugs, is imprisoned by his boss, ready for torture, and finds himself in the same cell as ERGO, who has been captured during the first big battle.

Quirkhardt and Ergo, although natural born enemies, escape from Pigfrog Command by dressing as washerwomen, unfortunately just as plucky Little Else is breaking into Pigfrog Command, coincidentally also disguised as a washerwoman in an attempt to rescue Ergo. She becomes imprisoned in the very cell from which Ergo and Quirkhardt have just escaped.

Eventually, helped by three flies called The Time Flies, -who travel through time in a converted thimble, Elsie escapes and declares her love for Ergo. They become engaged. Quirkardt, now captured by the slugs, spies against them in order to regain the favour of his General.

General Moundrot decides once and for all to attack the slug headquarters, situated in Nigel and Dotty’s tree house in Woodland Land. It is snowing heavily. The slugs and Trolls dig into the snow and watch as the Pigfrogs destroy their beloved tree house barracks, but Little Else bravely stands up to General Moundrot and is about to lead the slug army against the superior Pigfrog force when a piano falls from the sky and knocks General Moundrot out, causing his army to flee. The piano has fallen from one of the helicopters, which has arrived in the nick of time, bringing Ergo back from Pigfrog command.

Having been hit on the head, Moundrot becomes the nicest Pigfrog you could hope to meet, and insists that all Pigfrogs should join the scouts and girl guides and do at least one good turn every day.

Our epilogue shows Ergo and Elsie, years later, peacefully married, with two children, all living in Don’t Be So Ridiculous Valley, which is thus called because it is actually a hill, and hills go upwards, whereas valleys go downwards and along. Pessimists may say that hills go downwards, but they don’t, they go upwards. And Ergo can play the piano.