Just as English civil servant Henry
Brittingham-Brett explains to his parents that he is no longer
involved with his erstwhile girl friend Susan, she bursts into
Henry’s office and lavishes affection on him. Susan explains
to the Reverend and Mrs. Brittingham-Brett that she is married
to Henry’s best friend, Sir Philip Ashlowe, a British nobleman who
has little time for her after attending to his government affairs.
When Philip arrives home that day, Susan
complains about the effect his work commitment has had on their
relationship and persuades him to take a party of friends for a
vacation on their yacht. Having invited Henry and his parents
to dinner that evening, Susan shows the guests home movies of her
and Henry. Henry’s parents are disturbed when they see Susan
kissing Henry in nearly every scene and even more disturbed by
Philip’s naive suggestion that his best friend and wife are only
having “good clean fun.” Later, Henry’s mother suggests to the
Reverend that Susan is using their son to incite Philip’s jealousy.
Back at the Ashlowe’s, Susan uses her
sexy negligee to arouse Philip’s interest in a romantic evening, but
he is too busy to notice and kisses their dog Nelson instead of
Susan. When the couple set sail on the yacht, Susan hopes for
some time alone with Philip but finds that her industrious husband
is too consumed with helping out on board at all hours.
Needing a diversion, Susan calls Henry and entreats him to profess
his love for her in a rendezvous on the deck.
After days at sea, a violent storm sinks
the yacht, marooning Philip, Susan, Henry and Nelson, who became
separated from the other passengers, on an uninhabited tropical
island. The practical Philip immediately begins building a big
hut for him and Susan and a little bachelor hut for Henry.
Susan secretly hopes that life on the island will provide more time
to be with her husband; however, Philip is completely preoccupied
with the building construction. He even rigs an intercom
system between the huts with conch shells. Henry’s attempts to
aid Philip are clumsy and ignorant, causing both Susan and Philip to
scoff at him. Susan takes over gathering the oysters,
preparing meals and washing the clothes wearing only her black
undergarments, saving her evening gown for meals.
On the eve of the huts’ completion,
Susan sees her chance finally to be alone with her husband and
invites him to the hut for romance. Jealous of Susan’s
affection for her husband, Henry distracts Philip with a game of
chess. By the twenty-sixth day on the island Henry is so
desperate for female companionship that he kisses Susan, then
proposes that they have an affair. Susan, far from being
shocked, concludes that Philip would never suspect them because he
takes her for granted, but refuses Henry anyway. Sulking,
Henry threatens to tell Philip that he loves Susan and offer a
“lend-lease” situation. Since Philip has been generous enough
to share his shoes, Henry concludes that Philip might lend him his
wife as well. Infuriated by the immoral suggestion, Susan
warns that the proposal will only ruin their friendship.
Later that day, Susan is eavesdropping
when Henry tells Philip that they should share Susan. Philip
thinks the suggestion is deplorable, but Henry argues that Philip
neglects his wife and claims that he has been Susan’s lover for
several years. When Philip protests that Susan is too much of
a child to have had a lover, Henry falsely gives Philip his word of
honor that the affair has taken place. Susan resents being
referred to as a child and is incredulous that the suggestion does
not anger Philip more. When Susan denies having an affair with
Henry, Philip, the logical diplomat, resolves to find a solution to
the dilemma. As captain of the ship, Philip claims he has the
power to perform both marriages and divorces and asks Susan to state
her case for divorce. Susan alleges neglect and indifference,
citing Philip’s inability to recall the shade of the negligee with
which she last tried to seduce him. Philip concedes to a
divorce and suggests that Susan use her conscience to decide the
fate of their relationship. Leaving Henry alone at the big hut
with Susan, Philip moves to the little hut with Nelson.
Later that night, Philip sends Nelson
back to the big hut, knowing the dog will bark Henry out of the
couple’s home and force him to sleep outside. Soon after, when
Philip calls with the description of the negligee in question, he
once again endears himself to Susan. The next morning, the
competition between the two men has rejuvenated Philip’s interest in
his marriage. He and Susan are busy adoring one another, when
a man dressed as an island native surprises the group and ties up
Philip and Henry. They try to reason with him, but the native
utters gibberish and then drags Susan to the big hut. Once
inside the hut, Susan falls, causing the man to exclaim in Italian.
Susan then recognizes the man as Mario, the yacht’s chef, who
concocted the scheme to satiate his “primitive desires.” When
Susan laughs at Mario’s explanation, Henry and Philip assume she is
enjoying her captor’s attentions and blame each other for her
infidelity. Susan is pleased to see that she has finally riled
her husband’s anger when she exits the hut.
Suddenly a ship’s horn sounds off shore,
causing Mario to scream in English, revealing his true identity to
the men. Once safely on board the ship, Henry finally concedes
that there was no affair. Back in London, Henry, still
assuming the divorce was valid, arrives one night at the Ashlowe
house to ask Susan to marry him but finds Philip and Susan in their
nightclothes preparing to retire. Upon seeing that Susan is
knitting a baby sweater, Henry understands the nature of his defeat
and exits the house with a barking Nelson in tow.