Penelope the pug is completely content in her new forever home with Lady Diggleton. So when her beloved owner receives an invitation to meet the Queen at Windsor Castle - and an instruction to bring the pug along - Penelope couldn't be more pleased for her Lady's good fortune. However, once the two arrive at the castle, their fortune starts to seem less than fortunate. The Queen commands Penelope to befriend her own pup, a snooty dog named Duchess whose manners are most offensive, and who wants nothing to do with the poor pug. But when the Queen's prized Canis diamond ring goes missing and Duchess stands accused, Penelope - who knows the dog is innocent - must find a way to defend her. If the pug is certain that her fellow canine didn't commit the crime, though, can she clear Duchess's name by determining who did?