I'm studying the book Techniques of Differential Topology in Relativity by Roger Penrose and I'm stuck in an exercise he left to the reader. we say that the spacetime $M$ is strongly causal in $p$ if and only if there exists an event $q$ such that $q \prec p$ and for all events $x,y$ with $x \ll p$ and $q \ll y$ we have that $x \ll y$. I have to show that in such a situation if $q \ll p$, then there exists a closed trip (a timelike, future-oriented curve) through $p$. If anyone could help me with an answer or my thoughts below, I would be very grateful.
I tried many times but still can't figure out how. One thing that came to my mind is that we could extend the trip from $q$ to $p$ to a point $p'$ and then apply the condition of strong causality with the same $q$ but I'm not quite sure that it is ok to do that. If you want deeper contextualization, you can look at lemma 4.16 and remark 4.17 of the book, on pages 31 and 32.
Thanks in advance,
Bryant.