The narrator is referring to Leggatt as his alter ego--everything he wishes he could be but is not. The captain is only 27-years old, a young man to be in charge of men who are older and much more experienced than himself. The captain identifies with Leggatt, and through this identification he achieves a greater self-definition. The exact nature of the connection between the captain and Leggatt, however, is not clear. Leggatt has killed a man and is fleeing to escape punishment, but he may have committed this act in order to save his fellow crewmembers from danger. Through Leggatt, the captain becomes a stronger and more aggressive leader, but he also shows signs of instability.