On the night of April 9, 1865, the day
of General Robert E. Lee's surrender, revelers parade to the White
House, where President Abraham Lincoln appears on the balcony.
His request for the band to play "Dixie" is greeted by exhuberant
cheers.
On April 14, while the president watches
Laura Keene in Our American Cousin at Ford's Theatre, popular actor
John Wilkes Booth assassinates Lincoln and breaks his own leg
jumping to the stage. During a raging storm, Booth and his
comrade, David Herold, ride to a Maryland cabin where they ask for a
doctor. A black man directs them to the home of Dr. Samuel
Mudd who, not knowing Booth's identity, sets the leg.
The next day, while Dr. Mudd is away
delivering the baby of his former slaves, Buck and Aunt Rosabelle,
soldiers invade his home searching for Booth, and when one discovers
Dr. Mudd's young daughter Martha playing with Booth's boot, Dr. Mudd
is arrested for conspiracy in the assassination.
Although Booth is killed in Virginia,
eight persons are tried as conspirators by a military court because
the assassination has brought the country to the verge of hysteria.
After Assistant Secretary of War Erickson instructs the members of
the court martial not to let their judgment be troubled by
"pedantic" regard for the customary rules of evidence or by the
notion of reasonable doubt, the hooded prisoners are tried and three
are publicly hanged. Dr. Mudd is sentenced to life
imprisonment at the military prison at Ft. Jefferson in Dry
Tortugas, an island in the Gulf of Mexico near the Florida Keys,
which is surrounded by a moat filled with sharks.
Shunned by the prison doctor, Dr.
MacIntyre, and sadistically threatened by Sergeant Rankin, Dr. Mudd
is cheered to find Buck, now in the regiment of black guards, with
news from his wife Peggy that a judge, who has stated that Dr.
Mudd's conviction would not hold up in a civil court, has agreed to
reopen the case if Dr. Mudd can get to Key West. Dr. Mudd
plans a breakout with Buck but, during the attempt, Rankin has Buck
arrested and orders his men to bring back Dr. Mudd dead. The
soldiers shoot at Dr. Mudd on the prison's ledge and, when he falls
into the moat, the sharks are driven away by the gunfire. Dr.
Mudd reaches Peggy's boat, but Rankin, who has been ordered by his
commandant to bring him back alive, boards the boat with soldiers,
who fight and kill Peggy's elderly father, Colonel Dyer.
Rankin retrieves Dr. Mudd and throws him and Buck into a pit below
the prison.
When a yellow fever epidemic spreads and
Dr. MacIntyre is stricken, the commandant asks Dr. Mudd to help
without the hope of a reward. The doctor convinces the black
soldiers, who have barricaded themselves in the mess hall, to help,
but he gets the disease himself. When boats offshore with
doctors and medicine refuse to come nearer, Dr. Mudd, brandishing a
pistol, orders the black gun crew to shoot their cannon at them,
whereupon the ships head in. After the epidemic is controlled
and Dr. Mudd is out of danger, Rankin, whom the doctor cared for, is
the first to sign a letter to the President urging executive
clemency. The doctor returns home to Peggy and Martha with
Buck, who is overjoyed to greet Rosabelle and their twelve children.