"There's another angle to that," said Guy. "It'll make Pluto harder to find for the Martians, too. Since the radiation passes inward, the incoming ship may signal with a prearranged code, and the shield may be opened long enough for the ship to get a sight on Pluto. The barrier offers no resistance to material bodies." "Hm-m-m. We'll score another one for Guy," said Malcolm Greggor. "That'll be a nice nail in the ladder of success, young man. There's one more thing--are you thinking what I'm thinking?" "Perhaps. May I speak?" "Go ahead. Marian and Laura will not repeat it. Their interests are clear, and their trust has been accepted by the Patrol. All officials' wives are cleared to the Patrol's satisfaction since we know it is impossible to prevent us from mentioning small things from time to time." "Yes, indeed," said Marian. "Living with a man for years and years as we do, it would be hard to keep from knowing things. We hear a hint today, another next week, and a third a month from now. Adding them to something we heard last month, and we have a good idea of what the man is thinking of." "That's not all," laughed Greggor. "Wives have some sort of lucky mental control. Mine, confound it, can almost read my mind--and most of them can almost read their husbands' minds. So go ahead and speak." "I was thinking of a cruiser equipped with the barrier." "Is the equipment small enough?" "Certainly. The size of the barrier dictates the size of the equipment--within limits. Anything from a lifeship--say fifty feet long--to a super battlecraft like the _Orionad_--twelve hundred feet long--can be equipped." "Fine. And now as to this barring of radiation? How would the drive work?" "I don't know, not having had the opportunity of trying it out. I doubt that it will work." "Then the idea is not so good." "I think it fair enough for a trial." "But a ship without a drive is useless."