Ling Ling's estranged sister, Lang Lang, shows up at the Narutaki Detective agency unexpectedly. Six months prior, she had joined with Narutaki's rival, Le Bled, and ran away with him. Now, Le Bled has come for a showdown with Narutaki, and Lang Lang's visit is part of his plan. Lang Lang gasses Ling Ling and disguises herself as her sister, then tries to poison Narutaki. He, of course, is too smart for all that. When the plan is foiled, Le Bled appears, and tells Narutaki the only way to save Ling Ling is to defeat him in battle. The fight is joined, and Narutaki does save Ling Ling, but in doing so, Lang Lang and Le Bled are able to escape.

Narutaki meets with a scientist associate whom he helped earlier. Apparently scientists in the field of energy research have been disappearing then reappearing for a few days at a time. Narutaki starts to do some ground work on this mystery until Ling-Ling is attacked while trying to stop a masked man from kidnapping two prominent scientists. The masked man is the Phantom… and he made off with the scientists, but not before Ling-Ling managed to put a tracer on him. Will Narutaki face this foe?

Narutaki has to deal with his toughest case yet. Ling Ling is made at him, very mad, and the two aren't even on speaking terms. He might have another case in his lap searching for a missing cat, but that's going to be easy compared to overcoming Ling Ling's attitude.