Frixos, a bumbling individual who thinks he's a great detective, works at a detective agency. One day, he is assigned the task of finding the niece and sole heir of the wealthy shipowner Minas Giakoumis, who has been missing for a while.
As the primary and only identifying clue, there is a mole on the left buttock of the young woman. Frixos, in his quest for the mole, causes a commotion on the island of Kos, where there are suspicions that the missing girl might be, but without any concrete results.
However, a detective from a rival agency named Paul, who is also on the same mission, manages to succeed and discovers that the sought-after person is the girl that Frixos has fallen in love with, namely Mary, his assistant.