Helene, the daughter of the Count of Toulouse, has a secret rendezvous with her lover, Gaston. The Count killed Gaston's father in the civil war, but the young man will be willing to forgive him if he will agree to Gaston's marriage to Helene.
Crowds are celebrating the end of the Civil War. As the Count and his brother, Roger, are about to leave for the crusade, the Count extends his hand to Gaston and promises him the hand of his daughter in marriage. Gaston swears allegiance to the Count.
Roger however is jealous as he himself is in love with his own niece, Helene, and starts planning his own revenge. The Count gives Gaston his white coast and the two enter the chapel to pray to the success of the coming crusade.
Roger has hired an assassin and provides him with his final instructions: he should enter the chapel where two men are paying. He will recognize the Count by his white coat and should kill the mean who is not wearing a coat. The assassin does as he is ordered without realizing that he has struck down the wrong man. In order to save himself and Roger, the assassin informs that it was Gaston who ordered the murder. The papal legate orders Gaston to be exiled.
Four years later in Palestine
Roger, believing that he has caused the death of his brother, has become a hermit in Palestine to atone for his crime. Here he comes upon a pilgrim, dying of thirst, who urges him to help his fellow thirsty pilgrims and Roger agrees to do that. Helene, convinced of her lover's innocence, has come to Palestine to look for him. She recognizes the pilgrim as Raymond, Gaston's squire, and learns from him that Gaston in alive and held prisoner in Ramla. More pilgrims arrive and the crusaders' trumpets announce the arrival of the Count and his armies. He has survived the attempt assassination and has subsequently led the crusaders to the Holy Land. He asks the hermit to bless them, without realizing that this is his own brother. Roger asks to be allowed to join the Count.
The Emir of Ramla, who is holding Gaston, has also captured Helene. The lovers meet and try to fly together but are caught by the Emir's guards.
Helene is being held in the Emir's Harem. He informs her that the Christians are marching on the city and warns her that if they enter Ramla, he will kill her. Gaston, who has succeeded in freeing himself, finds Helene but almost at the same time the crusaders, led by the Count, burst in. The Count is horrified to see his murderer together with his daughter and orders Gaston's execution.
Gaston is led back to prison, humiliated by the crowd. He begs forgiveness but to no avail. His execution will take place the following morning.
The crusaders camp in the valley of Jehoshaphat
Before the battle to capture Jerusalem, the crusader army prays for victory. Roger reunites Gaston and Helene for a final farewell. Moved by his knowledge that Gaston is innocent, Roger allows him to regain his honor by taking part in the battle.
Following the crusaders' victory, the Count thanks the mysterious knight who has fought with great valor. Everyone is astonished when the knight reveals himself to be Gaston. Roger, mortally wounded, reveals his true identity and admits that it was him and not Gaston who was responsible foe the Count's attempted murder. He begs forgiveness and asks to see Jerusalem one last time.