As a cargo ship is about to depart, a man runs along the pier, begging to be taken on board. The captain agrees. The only passengers are the captain's niece, Marie, accompanied by her little boy. The man is taciturn, we know nothing about him, but he watches the child playing. A message is received. A murderous doctor has fled on a boat. The captain suspects the stranger. Marie defends him. A serious illness strikes down the child. The mother begs the passenger. He is indeed a doctor and manages to save the child. The captain then receives a moving letter and offers to drop the man off as soon as possible. He agrees, but the child also gives him a letter. Marie absolves him of the crime and adds that, forever grateful, she will wait for him in Rio.