Simon is a highly talented and highly paid surgeon. Or at least, he was, until he sprang his sister form an Alliance institute and has been running ever since.
Simon has led a sheltered life and is not wise in the ways of the border regions of space, but he has two things going for him: his tenacious mind, and his love for his sister, for whom he would, and does, risk everything.
Simon: "Now River, stay behind the others. If there's fighting, you drop to the floor and run away. It's okay to leave them to die."