Haunted by the memory of Walter Holderlin, a soldier he killed during World War I, French musician Paul Renard (Phillips Holmes) confesses to a priest (Frank Sheridan), who grants him absolution. Using the address on a letter he found on the dead man's body, Paul then travels to Germany to find his family.　　As anti-French sentiment continues to permeate Germany, Dr. Holderlin (Lionel Barrymore) initially refuses to welcome Paul into his home, but changes his mind when his son's fiancée Elsa identifies him as the man who has been leaving flowers on Walter's grave. Rather than reveal the real connection between them, Paul tells the Holderlin family he was a friend of their son, who attended the same musical conservatory he did.　　Although the hostile townspeople and local gossips disapprove, the Holderlins befriend Paul, who finds himself falling in love with Elsa (Nancy Carroll). When she shows Paul her former fiancé's bedroom, he becomes distraught and tells her the truth. She convinces him not to confess to Walter's parents, who have embraced him as their second son, and Paul agrees to forego easing his conscience and stays with his adopted family. Dr. Holderlin presents Walter's violin to Paul, who plays it while Elsa accompanies him on the piano.　　The film's original title, The Man I Killed, was changed to The Fifth Commandment to avoid giving "wrong impressions in the minds of the public about the character of the story." It ultimately was released as Broken Lullaby.“我说的不清楚么？我的意思是说，我的身上，也还有一眼生命之泉啊。”楚阳说道：“我就是用身上这一眼生命之泉，令九重天大陆的那一眼生命之泉重新焕发了生机。就现在的情况而言，就算是你们这里已经渐渐干涸了，但实际上还没有完全干涸……也就还是生命之泉，只是流溢出来的泉水少到极点而已，这样说来，这世间至少有三眼生命之泉存在，换言之，你之前关于生命之泉唯一性的说法，在这里说不通了。我这么说，你明白了么？”