At the beginning of the story, the mouse Hermux Tantamoq is a watchmaker in Pinchester, a Manhattan-like metropolis inhabited by rodents, birds, and mustelids.

Investigating this, Hermux learns that Mennus, in partnership with sub-antagonist Tucka Mertslin, seeks to patent a rejuvenation formula obtained by Linka's client, Dr. Turfip Dandiffer.

To maintain control of Tucka Mertslin, Mennus memorizes and destroys the formula; but by an inept use thereof, reduces himself to infancy.

Some days later, Hermux approaches Linka, intending to propose marriage, but finds her already engaged to Dandiffer.

It was then taken up by Penguin Putnam, who for world-wide rights paid Hoeye what at the time was "the record sum received for a children's book".