Learning a vacancy has arisen in the sleepy Cornish village of Portwenn, Martin promptly applies and gets the job, despite opposition from local schoolteacher Louisa.

A nasty stomach bug sweeps through Portwenn and the doctor suspects the local water supply is to blame, taking to the airwaves in a bid to warn everyone. Meanwhile, Al remains determined to leave the plumbing business and attend college, prompting an argument with Bert.