Episode 74 of The Trigan Empire
Chase For A Traitor
aka Het verraad van Hipsos (Dutch title)
The Betrayal of Hipsos (Dutch title, translated)
Written by Ken Roscoe
Illustrated by Gerry Wood
Chase For A Traitor was originally published in 6 instalments in issues 860 (8 July 1978) to 865 (12 August 1978) of Look and Learn magazine.
To date it has not been reprinted in English.
Plot summary (Dutch)
MediaFire via British Comics Compilations