 How did Ninian, Raymond, and the other cousins go back in time?
No one, least of all Martin, could dispute that a man's life should be guarded by his kin—but by those who hadn't been born yet? Nobody in the neighborhood was surprised when Martin's mother disappeared and Ninian came to take care of him. Besides, if she really was his great-great-grand-daughter, as she said, why would she tell him to call her " Aunt Ninian "? But Ninian didn't know that and she went into a real tizzy, babbling that Martin had been sick and would make up the work. When it became clear that his mother was never going to show up again, Ninian bought one of those smallish, almost identical houses that mushroom on the fringes of a city after every war, particularly where intensive bombing has created a number of desirable building sites. Martin was told to call him Uncle Raymond. From time to time, there were other visitors—Uncles Ives and Bartholomew and Olaf, Aunts Ottillie and Grania and Lalage, and many more—all cousins to one another, he was told, all descendants of his. The non-glass part of the house was of neat, natural-toned wood, with a neat green lawn in front and a neat parti-colored garden in back. It was then that Martin began to realize that either the whole lot of them were insane, or what Ninian had told him at first was the truth. When Martin was sixteen, Raymond took him aside for the talk Ninian had promised five years before.
 They bribed the assistant for the plans and blackmailed or tortured someone to build the time transmitter for them.
 They bribed the assistant for the plans and blackmailed or tortured someone to build the time transmitter for them.  Professor Farkas' assistant sent them back in time using the time transmitter after they gave him a bribe.  They bribed the assistant for the plans and hired a gadget enthusiast to build the time transmitter for them.  Professor Farkas sent them back in time with the time transmitter.