Portwenn is buzzing with the news of the engagement of Dr Martin Ellingham and Headmistress Louisa Glasson. Mushrooms are the cause of an outbreak of aspergillosis in the village. Bert Large, postman Dave and restaurant chef Mick Mabley are among the victims. Bert Large's ill health is not his only problem. His restaurant is in financial trouble. Son Al decides it is time to take action to save the business.