Cnaiur forgets that he is supposed to be hunting Moenghus. Instead, he is sitting in some random city at the Dunyain's request, babysitting Conphas.
That, or he is forgetting that Kellhus wants to kill him, and he realizes that his stationing there is a deathtrap.
Either/or, i can't remember which one he finally settles on in his moment of revelation.