Clara Harris moved to Washington D.C. in 1861 with her family, after her father Ira Harris was elected Senator for the state of New York. Over the next few years she became friends with the first lady, Mary Todd Lincoln, due to her father's friendship with the President. Clara attended a few plays with Mary Todd and was present the night of Lincoln's last public address, a speech from the White House window above the main door. It was her friendship with Mary Todd Lincoln that drew the invitation to the Ford's Theatre on Good Friday. After being turned down by multiple people, the first lady offered seats to Clara and her fiance Major Henry Rathbone. The couple gladly accepted.
The White House carriage arrived at the home of Senator Harris a little after 8 p.m. Clara and Henry joined the President and his wife, then the foursome traveled the last few blocks to Ford's Theatre.
That night Clara sat in a chair to the right of Mary Todd Lincoln, with her fiance Henry a little behind her and to the right on a sofa in the corner of the Presidential box. The evening went along charmingly until the attack of John Wilkes Booth. Upon the clash of the gun and seeing Henry in melee with the attacker, Clara was one of the first to call out for help, yelling "Stop that man! Won't somebody stop that man!" as Booth landed on the stage below and escaped out the back of the theatre.
Mary Todd wailed in agony after realizing what had transpired. Clara moved in to console her friend. After doctors arrived and determined it was necessary to move the President, Clara escorted Mrs. Lincoln across the street to the Petersen house. Unfortunately, Clara's attention was soon drawn to Henry. He'd been severely stabbed by Booth and was profusely bleeding. Clara attempted to the stop the bleeding by wrapping a hankerchief around his upper arm, but the blood loss was too extreme and Henry fainted in the hallway. General James R. O'Beirne, the provost marshal of D.C., arrived near this time and noticing Henry's condition, helped the Major and Clara into a carriage, sending them back to the home of Senator Harris.
Upon arrival, Henry was assisted into the home and a call for the family physician, Dr. G.W. Pope was made. When he arrived, Pope later noted that "the family and servants were in great excitement and distress", but Clara "retained sufficient calmness to render assistance and keep order." The doctor quickly ascertained the severity of Henry's wound noting, "a deep, narrow dagger thrust, clean through the inner bicep of the left upper arm." Dr. Pope cleaned and dressed the wound, with Clara standing by assisting with "water, bandages, towels". He was impressed by Clara and wondered "whether any of our modern society women would have been equal to such an emergeny."
After the assassination, Henry and Clara continued their engagement and were married July 11, 1867 in their hometown of Albany, NY. The couple lived in Washington D.C. for much of the time after that, with extended visits to Europe. Clara gave birth to the couples first child, Henry Riggs Rathbone on February 12, 1870, the same birthday as Abraham Lincoln. It was the same year that Henry officially resigned his commission in the Army. He never found regular work after that, but due to a large inheritance from his father's passing when he was a young boy, the family was very affluent.
As the years passed, the tragedy of assassination night plagued Henry mentally. While his arm wound was a physical reminder, Henry struggled emotionally with the failure to protect Abraham Lincoln and catch John Wilkes Booth. He became more reclusive and introverted, relying on the education and social skills of Clara to keep the family in good standing. By late 1872, seven years after the assassination, Henry and Clara had three children and from outward appearances were doing well. Close friends however noticed Henry's odd behavior increasing. In addition, Henry started suffering from Dyspepsia, a chronic indigestion.
The large family of five continued their travel overseas, educating the children and also reviewing new medicine for Henry's dyspepsia. In 1883 the family moved to Hanover, Germany and on Sunday, December 23 of that year, Henry's ailments got the best of him. He awoke in the early morning and approached the door of his children's bedroom. He was carrying a gun and asking for the children's nanny to unlock the door. Clara, woken by the noise, begged her husband to come back to the bedroom with her. Henry agreed after Clara's pleading and as they returned to the bedroom, Clara quickly called out to the Nanny, who was her sister, "Lock the door and save the children; there is going to be dreadful work."
Henry then grabbed Clara by the arm and dragged her into the bedroom. The nanny and the children heard yelling and struggling for a short while, until Clara screamed and two gunshots rang out. The nanny ran into the room to find her sister, Clara, lying bloodied on the bed. With bullet wounds and multiple knife wounds, Clara died within minutes. Her last words were, "He has killed us both at last."
Henry was committed to a nearby insane asylum in Hildesheim, Germany. He remained there for twenty-eight years, until his death on August 14, 1911.
The three Rathbone children went to live with Clara's brother, Colonel William H. Harris in Cleveland, Ohio.