Lost in Space S01 E23 The Space Trader

"A space colony family struggles to survive when their ship is hopelessly thrown off course."

After the entire Robinson food supply is wiped out in a freak storm a trader arrives to trade food for equipment the Robinson's possess. Dr. Smith trades the robot for food and hoards the supplies for himself. Later, after the Robinson's discover his transaction he gets the robot back but in exchange for his own self. The Trader then wants to take Smith as a slave, to another planet.