 The captain of the crew of Serenity is Malcolm " Mal " Reynolds ( Nathan Fillion ) and the episode " Serenity " establishes that the captain and his first mate Zoe Washburne ( Gina Torres ) are veteran " Browncoats " of the Unification War , a failed attempt by the outlying worlds to resist the Alliance 's assertion of control . A later episode , titled " Out of Gas " , reveals that Mal bought the spaceship Serenity to continue living beyond Alliance control . Much of the crew 's work consists of cargo runs or smuggling . One of the main story arcs is that of River Tam ( Summer Glau ) and her brother Simon ( Sean Maher ) . River is a child prodigy , whose brain was subjected to experiments at the hands of Alliance scientists at a secret government institution . As a result , she displays schizophrenia and often hears voices . It is later revealed that she is a " reader " , one who possesses telepathic abilities . Simon gave up a career as a highly successful trauma surgeon to rescue her from the Alliance , and as a result of this rescue they are both wanted fugitives . In the original pilot " Serenity " , Simon joins the crew as a paying passenger with River smuggled on board as cargo . As Whedon states in an episodic DVD commentary , every show he does is about creating family . By the last episode , " Objects in Space " , the fractured character of River has finally become whole , partly because the others decided to accept her into their " family " on the ship . 
