S02E147: The Mermaid That Disappeared in the Midnight Sun

Fujiko, wearing not a stitch of clothing, is the model for a statue of a mermaid, carved from quartz crystal. With a heave, a pile of bills are laid before the sculptor, Vingel, by the mayor of a town who says he wants to make the mermaid into a tourist attraction, and Vingel sells it to him. When Fujiko cries to Lupin to get it back, he makes his entrance. The boxcar of the transport train carrying the statue has a special coupling mechanism, and stealing it will require a little engineering. Lupin's fanciful notion is a cold and clear one.