 Why can't the square-built man defend Trella against the men attacking her?
Trella feared she was in for trouble even before Motwick's head dropped forward on his arms in a drunken stupor. A woman could not possibly make her way through these streets alone to the better section of town, especially one clad in a silvery evening dress. Perhaps she could call one of Motwick's friends; she had no one on Ganymede she could call a real friend herself. Trella swung with her whole body, and slapped him so hard he nearly fell from his chair. Her protector was obviously unwilling, but the dark man, faced with his massiveness, took no chances. The dark man moved in on Trella again as Kregg overtook his quarry and swung a huge fist like a sledgehammer. The dark man, who had grabbed Trella's arm, released her and ran for the door. Trella ran to the unconscious Motwick's side. He followed Trella out the door of the Golden Satellite and fell in step beside her. It was peculiarly inappropriate, but not unbelievable, that the strongest and most agile man on Ganymede should be a coward. Trella could get a cab from here, but the Stellar Hotel wasn't far. Trella had the desk clerk call a cab to deliver the unconscious Motwick to his home. For some reason she decided against telling him that the assignment on which she had come to the Jupiter system was to gather his own father's notebooks and take them back to Earth. Motwick was an irresponsible playboy whom Trella had known briefly on Earth, and Trella was glad to dispense with his company for the remaining three weeks before the spaceship blasted off. The ship that they boarded on Moon Nine was one of the newer ships that could attain a hundred-mile-per-second velocity and take a hyperbolic path to Earth, but it would still require fifty-four days to make the trip. The Cometfire swung around great Jupiter in an opening arc and plummeted ever more swiftly toward the tight circles of the inner planets. There were four crew members and three passengers aboard the ship's tiny personnel sphere, and Trella was thrown with Quest almost constantly. She told him only that she was a messenger, sent out to Ganymede to pick up some important papers and take them back to Earth. Her employer had impressed upon her that her mission was confidential, but surely Dom Blessing could not object to Dr. Mansard's son knowing about it. When it was found at last, he sent Trella, his most trusted secretary, to Ganymede to bring back to him the notebooks found there.
 His programming does not allow it
 His programming does not allow it  He is a strict pacifist  He is full of cowardice  He is secretly collaborating with Trella's attackers