Rox is mobilized to catch the mysterious perpetrators of a serious of recent mystery thefts from well-guarded museums, preferably before the discovery of the latest causes diplomatic embarrassment at a prestigious exhibition opening. The only clue leads to Pingi Park, a small private zoo. Xavier and Olivi go undercover and find enough clues, combined with Rick's crime scenes analysis, to work out the thief used Billy, the tame monkey trained by a zoo keeper to retrieve things. Yet the monkey-coach isn't the actual robber.
