Offenbach concerns himself with neither historical accuracy nor with the fate of the nations, but uses an old legend as the subject of a gay operetta in which he pokes fun at the celebrities of his day.

The beautiful Helen of the title is none other than our friend Helen of Troy, Queen of Sparta in Ancient Greece, whose legendry beauty "launched a thousand ships".

The Prologue to the opera is set on Mount Ida where Paris, disguised as a shepherd, selects Venus as the fairest of the goddesses by awarding her a golden apple.  As a reward, Venus promises him the love of the most beautiful women on earth.

The operetta itself opens in Sparta where Calchas, the High Priest, is making preparations for the annual Adonis ceremony.  There is a lamentable lack of interest in the ceremony on the part of the general population.  In fact the sole devotee is beautiful Queen Helen herself, who attends the temple only to keep on the right side of Venus, especially as she has heard of the goddess' promise to Paris and is waiting for the "shepherd" to arrive.  

After assurance of help from Calchas, Helen enters the temple and, whilst the ceremony is taking place, Paris arrives.  Calchas engineers a meeting between Paris and Helen and also promises his assistance in getting rid of Helen's husband, King Menelaus.  King Menelaus arrives with his guests, the three kings, Ajax, Achilles,  and Agamemnon.  With the help of Philocomus, his assistant, Calchas arranges a sign.  It is proclaimed that Menelaus spend a month in Crete and everybody, especially Helen, cheerfully sends him off on his journey.

Although Menelaus is now out of the way, things do not go well since neither Helen nor Paris will make the first move towards meeting one another.  With some contrivance they are at last brought together and rapidly fall in love.  Unfortunately, their rapture is short-lived as they are rudely interrupted by the unexpected return of Menelaus who angrily sends Paris away, mush to Helen's disappointment and annoyance.

A week later at the seaside resort of Nauplia, relations between Helen and Menelaus are still very strained; he is upset at her waywardness while she feels that she has lost all hope of ever seeing Paris again.  Calchas once again comes to her assistance and ushers Paris into her presence.  She is delighted to learn that the two of them have concocted a plan to ensure that she will belong to Paris forever.  Meanwhile, Menelaus has also concocted a plan, one for keeping Helen out of mischief; she is to make a pilgrimage to the goddess' shrine on the island of Cythera.  He knows that she will be quite safe as Venus' Chief Augur is to accompany her.  Scheming Calchas is behind both plans however, and it will come as no surprise that in the end love follows its true course.