Major Caldwell believes Jake Webster was the real target when an elderly flower lady is killed outside of Jake's Bar. However, Jake suspects another motive. He decides to investigate one of the three mourners at the old woman's funeral.

Jake uses a painting to find a royal emerald stolen by a convict, the painter of the portrait, in 1886. The painting leads him to a tunnel under the Hofburg Palace filled with plaster models of monuments. Jake must contend with several other crooks who are also after the emerald.