A spaced mystery:

"Trust only Jones," Captain Hero’s commander told him when he gave him the mission to rescue defecting General Bungo from the anthropophagous alien Djerki who had taken over the Luna Colony base on the moon. "Though he looks human, he is a robo-android who always tells the truth. There is a traitor on your team, but we don’t know who. Jones has spent two years on the lunar base, knows the General, and will be the first to recognize if anything goes wrong. Your second pilot Smith is also a truthful robo-android. He was provided to us for this mission by the government of the Luna Colony. Sergeant Zorch is a Djerk, an alien humanoid working for us as your Indian Scout, but still a compulsive man-eater, and a compulsive Djerki liar as well. He cannot be left alone with a human, particularly General Bungo.

"You must take the fast shuttle, which carries only four people, and make the trip from the orbital colony at the L-5 Lagrange point back and forth as few times as it takes to bring back General Bungo and all of your team. Your problem is like the man who must carry the fox, the goose, and the grain across the river in a boat too small for all. You cannot put a human alone with a Djerk, and you cannot put General Bungo alone with the traitor, who might kill him to prevent his defection."

With Jones in the cockpit beside him, and Smith and Zorch in the separate passenger cabin behind, Captain Hero departed for the moon.

"As agent of the Luna Colony government, I can get in alone and bring out General Bungo," Smith told Captain Hero on the intercom. "We have fuel for only two trips to the base and back. If you stay behind, I can fly General Bungo to safety with Jones and Zorch in the cabin, then come back to pick you up."

"I served in the Luna Colony as a Security Officer, and worked close to General Bungo," said Jones. "We used to enjoy watching earthrise together while we discussed his dreams of defecting. I know his world and his routine better than anyone else; I alone can get to General Bungo and get him out alive. Then you may leave me behind, and come back to pick me up on the second trip."

"I served in the Colony also, in the occupation forces," said Zorch the Djerk, "and I knew who belonged to whom in the Colony government. Smith is a re-programmed agent for the Djerki, and will stop at nothing to kill General Bungo. By destroying Smith, we three can rescue General Bungo and fly out in one trip."

Thereby able to identify the traitor, Captain Hero took the necessary steps to accomplish the mission. How did he know who the traitor was, and what was done about him?