Time is a fickle thing.
For most of them, time passes in a linear fashion. Seasons march on, each year advances inorexibly, age and death coming to most (though death slower in Beqanna than most places). But for him, time is a web and he is the spider. For Cagney time is malleable, and he has lived almost exclusively in dark pockets of time for long enough that finding the real timeline is like swimming upstream against a great current, or navigating a particularly tricky maze.
In the end it is two bright life-lines in the time web that bring Cagney back into the same stream as everyone else; his father a solid presence as ever in his life, and his daughter with her bright light and resemblance to her mother. Their timelines are clear enough that he knows he has found the right time-place, but nothing else is right. Nothing is as he remembers it, nothing is as it should be, and without Brennen and Kellyn, Cagney might well have simply returned to the unfathomable shelter of no-time, and been lost forever.
(He has no purpose without her, anyway, and her light has been extinguished in this time. Nothing has changed.)
The time traveler tracks his father to the very edge of this new world, where he is confronted by the impassable stretch of water. In his not-vision he can see that the water ebbs and flows here, and time will reveal a walkable passage, and he is tempted to tug a line here, and push a thing there, to bring that time to now; but he is weary from finding this time-place at all, and so instead he waits at the mainland edge of the water, still and quiet enough to be dead. And time does not fail him, as it has ever not failed him, and he crosses to Ischia at low-tide, to stand on the warm shores of a place as different from the Tundra as anyone could ever have dreamed.
(Everything has changed. They say time heals all wounds, and he might not prove the exception to the rule after all.)