Rum Affair.
Tina Rossi, the world's leading coloratura soprano, has travelled to Edinburgh, ostensibly to sing in the Festival, but in reality to meet her lover, top scientist Kenneth Holmes. Instead of finding Kenneth at their rendezvous, she discovers an unknown corpse. At this moment Johnson Johnson, a famous but enigmatic portrait painter turns up. Dolly is about to sail in a race to the Hebrides where Holmes was conducting his top-secret research to discover more about his disappearance.