Mycroft has a missing agent; the stepdaughter of Lord Wexford Foyle wants a pearl brooch authenticated. Sherlock Holmes has little interest in either until he learns the gem is the Jacobite Rose, a royal treasure. Reading Debrett's Peerage, Holmes discovers Lord Foyle has a brother who is known as a craftsman in gold. Three strange clues - the drawing of a rose, fish scales and a fragment of pine resin - discovered at the last known locus of the missing man begin to link the two cases.