When bank teller Peter Stirling draws whispers and
funny looks from his customers, bank manager Munroe asks him to
explain. Stirling states that it all began when he was
stationed in Burma. Second Lieutenant Stirling is separated
from his platoon behind Japanese lines, and there he encounters
Francis, a talking Army mule. Francis carries the wounded
Stirling to safety; but after Stirling credits the mule with his
rescue, he is committed to the psychiatric ward and assigned to make
baskets under the watchful eye of his nurse, Valerie Humpert.
Eventually, Stirling admits that he must have been mistaken and is
released to active duty.
Soon after, Maureen Gelder, a beautiful French woman,
is given sanctuary on the base. She tells the officers that
she was separated from her father when the Japanese invaded.
Then Stirling, who has absolutely no qualifications, is assigned to
duty as a clerk in the Intelligence department. The next day,
Stirling finds a message from Francis on his desk. Not knowing
that the other men put it there as a joke, Stirling rushes off to
see the mule. At first, Francis refuses to talk to Stirling,
but then reveals that the Japanese have set up an observation post
nearby and suggests that Stirling capture it with his help.
That night, Francis leads a terrified Stirling to the
post, and they capture the two Japanese who are manning it.
Later, the commander demands to know how Stirling learned about the
post, and when he says Francis told him, he winds up back on the
psychiatric ward. The psychiatrist diagnoses battle fatigue
and recommends activity.
When Stirling is assigned to lead a group of soldiers
searching for a Japanese patrol, Francis again provides help.
On the mule's advice, the men set a trap for the Japanese, and
Stirling is returned to the psychiatric ward. He is visited by
Maureen, who seems romantically interested in him, and tells her
about Francis. Francis now tells Stirling that enemy bombers
will attack the base at a specific time. Stirling frantically
tries to convince the commander to prepare. Eventually,
because of Stirling's past record, the commander accedes to his
demands. After the Japanese attack, Stirling credits Francis
and is forced to take up basket weaving on the psychiatric ward.
One day, Stirling is visited by Commanding General
Stevens. Determined to finally prove his sanity, Stirling
drags Stevens to see Francis, who refuses to speak. Stirling
then suggests that as Francis is an Army mule, he might speak if
Stevens ordered him to do so. After Francis finally speaks,
Stevens apologizes to Stirling and orders him to be released from
the hospital.
Later, over Tokyo radio, a woman makes fun of the
soldiers for believing in a talking mule. The press arrive,
and Stevens orders Stirling to bring Francis to meet them.
Meanwhile, the officers try to figure out how the Japanese learned
about Francis. Stirling reveals that Maureen knew about the
mule. Colonel Hooker, Stirling's immediate supervisor, then
explains that they suspected Maureen was a spy and purposely
assigned a naïve officer to trap her. When Maureen accuses
Stirling of passing the information to the enemy, Francis speaks in
his defense.
Afterward, Francis is flown to Washington. When
his plane crashes over Kentucky, the crew parachutes to safety, but
Francis refuses to leave. Stirling tells Munroe that he then
searched Kentucky until he found Francis, who is now living with
him. When Munroe expresses his incredulity, Stirling brings
him home to meet Francis.