 Adam Baldwin as Jayne Cobb — a mercenary . He and Mal met on opposite sides of a rivalry ; Mal , while held at gunpoint , offered Jayne his own bunk and a higher cut than his current employer , so he turned coat and shot his then @-@ partners . In the original Pilot " Serenity " he intimates to Mal that he did not betray him because " The money wasn 't good enough , " however previously he had pointedly asked the Alliance agent whether he would be required to turn on the captain to help him , and in " Ariel " defends his actions alerting the authorities regarding Simon and River by claiming he had not intended to betray Mal . He is someone who can be depended on in a fight . He tends to act like a " <unk> " who thinks he is the smartest person in space , but occasional hints of intelligence peek through this façade , giving the impression that he acts dumber than he is . As Whedon states several times , Jayne is the man who will ask the questions that no one else wants to . Even though he is a macho character , he has shown a particularly intense fear of Reavers , more so than the rest of the crew . Despite his amoral mercenary persona , he sends a significant portion of his income to his mother , again suggesting that there is more to his character than what he presents to the rest of the crew . 
