For me, this is a special author with his own unique literary style, with magnificent works of the science fiction genre.
In this story, one time traveler, when he got to the Upper Cretaceous period, expected to meet anything there, but not two children, and even from Mars! After that, everything seems to develop as expected: after experiencing dangerous adventures together, the brother and sister became attached to our traveler... Although everything is not quite that simple. After all, time and distance did not leave them any chance to continue their friendship. Or is there still a small chance? Very interesting reading.
Again, I almost got the annotation out. I love this business ;-)