The whole Ardath family is collected together to discuss the proposed marriage between Margaret and Robert Ogden, a British citizen. The consensus of opinion is that the match is desirable in every way. The old Colonel says that in case of war the children of such a match would make fine soldiers. This frightens Margaret, as all her life she has had a dislike for war. Dr. Ardath is on his way to an important conference and gets started on his favorite subject, the heart. He tells those present of a wonderful new drug that has been found by a Russian student who used it to depress the action of his heart to get out of military service and who, taking an overdose, was killed. The story makes a strong impression on Margaret and she falls into a troubled sleep. A boy is born to Margaret. All through his childhood he shows signs of being a fighter, and when he grows up he wants to join the National Guard. Margaret is forced to give in and consents. Shortly afterward, Donald, the son, becomes engaged to Patricia Landon. His father is called to England on business and he is put in full charge of the firm. A few months afterward, a letter comes from the other side saying that his father had enlisted when the war broke out. Margaret takes the news seriously, and Dr. Ardath is sent for. The doctor leaves his case of medicines on the table and Margaret sees the cardiac depressant in it. The idea at once comes to her that it might be of use to her in case the government should draft her son, so she takes the vial. Then comes the news that the United States and Mexico are going to war. She at once makes use of the medicine and so affects the action of Donald's heart that he is rejected. The boy is heartbroken and goes to tell Patricia. He receives a cold reception and later the girl's mother argues with her until she agrees to break the engagement owing to Donald's poor health. Donald takes to drink. His mother is heartbroken, as she thinks that she is to blame for it all, and hesitates to tell the boy that Patricia has married another man. Then the news comes that Robert is wounded. Dr. Ardath returns and upon examining Donald, says that his heart is all right. They telephone the other doctor and from what he says, the doctor knows that some of the cardiac depressant must have been used. Donald, when he finds this out, rushes to accuse his mother. She goes to get the drug, but takes it herself instead. As Margaret comes to the head of the stairs she overhears Donald reading a telegram from Europe saying that her husband is dead. With that she falls over and, with a bump Margaret wakes from her terrible dream. She is delighted to find that her husband is really alive and as the picture closes she says that at last she is convinced that one's duty to one's country is the highest, and says that she will never oppose Robert's responding to his country's call.