The clan had a plan. Their fortune had been foretold in a great book: nay, the book. Mr Bunnsy Has An Adventure showed them utopia: rats living in harmony with humans.
They had the fortune (or misfortune?) of meeting Maurice after he too had acquired a Gaspodic level of thought process. With him they embarked on a series of misadventures, utilising the skills of Keith the Piper they became the type of plague of rats experienced on Roundworld in Hamelin. Keith was the Piper and once he'd "got rid" of the rats and been paid, the local townsfolk from towns all across the Sto Plains would have been astonished to know that they all met up round the nearest bend and counted up and divvied out the money.
The Clan nearly came to grief in Bad Blintz, but through ingenuity and bravery they realised their dreams of utopia: now they truly do live in harmony with humans.