The Butterfly Effect

Jonny, Kirsty and Yo-less make it back from the 1940s, but Wobbler and Bigmac are still there. To make things worse the mysterious Sir Walter turns up and talks about the ""butterfly effect"", basically: little things in the past have big consequences. To make things worse he then reveals that something Jonny or his friends did in the past has caused Jonny never to be born!