The Quality Street Factory is fizzing with the news that the King and Queen and the two young princesses, Elizabeth and Margaret Rose, are going to visit the Mackintosh Factory where the country's favourite wrapped chocolate is made. The factory floor is heady with excitement but plans are dealt a blow when a much loved staff member is the victim of a poisoning incident.

Everyone is under suspicion, which only adds to Reenie Calder's woes, anxious that her new promotion has only made her stick out even more like a sore thumb. Can she and her friends, Mary and Diana, get their heads together and find the malicious troublemaker before something unthinkable happens?