Stephen Ashe, a famous criminal lawyer, lives in San Francisco and is adored by his free-spirited daughter Jan.
One day, Stephen, a freethinker who drinks too heavily and hates everyone in his family except for Jan, is invited by Grandma Ashe to a family dinner. After extending the invitation, the snobbish Grandma Ashe warns Jan not to let Stephen drink that evening. As feared, Stephen does not heed her request, and she and the rest of the family are shocked when he arrives with Ace Wilfong, an underworld character whom Stephen is defending in a murder trial. Soon after Stephen introduces Ace to his family, he is appalled at their lack of hospitality, and he leaves with Ace. Jan, also upset with her family's reaction to Ace, follows them, leaving her stolid fiancé, Dwight Winthrop, behind. While driving home, Jan tells Ace that he is the first truly exciting man that she has met. Their drive is interrupted when their windshield is sprayed by bullets from the Hardy mob, who want to kill Ace. Ace and Jan begin a romance which results in Ace asking Stephen for permission to marry his daughter. Stephen denies Ace's request, but Jan continues to see him regardless. When Stephen comes home drunk from a casino bust one night, he and Jan make a pact to rid themselves of their vices. While Stephen promises to stop drinking, Jan swears off the troublesome Ace. Father and daughter then take a vacation in the mountains to get away from the temptations at home, but as soon as they return, they fall into their past habits. Jan's romance with Ace turns violent when he scolds her for leaving him. After attacking her, Ace demands that she marry him. Jan refuses and returns to Dwight, who has been attending Grandma Ashe on her deathbed. When Dwight witnesses Ace manhandling Jan, he becomes outraged and shoots him. Dwight then calls the police himself and, in order to protect Jan, tells them that he shot Ace over a gambling debt. At his trial, Dwight's defense flounders until Stephen arrives and takes over. Stephen immediately calls the killing a result of temporary insanity, and then declares that it is not Dwight who should be on trial, but he himself. Stephen argues that were it not for his allowing Jan to see Ace to begin with, the whole tragic affair could have been prevented. After calling Jan to the witness stand, Stephen becomes so impassioned that he collapses, suffers a heart attack and dies in his daughter's arms.
The jury subsequently finds Dwight innocent, and he and Jan leave for New York, where they plan to begin life anew.