It's the autumn of 1805, and the Prince of Wales, frightened by threatening letters, has moved with his entourage to Brighton to escape the unknown menace. There, during a walk on the beach, his friend Beau Brummell discovers the body of a young lady, whose identity he's moved to discover. Before he can make much progress, Sir Simon, an obnoxious parvenu who has ingratiated himself as the prince's food taster, samples a new blend of snuff belonging to Lord Petersham at a dinner party with fatal results. Believing he was the intended victim, Prinny orders Beau to find out who put the poisoned snuff in Lord Petersham's box. Petersham himself is a suspect, and it will take the intervention of Brummell and his pet, Chakkri, "the only Siamese cat in England," to clear the lord's name. In the end, the chivalrous Beau risks social ruin to bring the real murderer to justice.