Commander Keen in Goodbye, Galaxy
It consists of the fifth and sixth episodes of the "Commander Keen" series , though they are numbered as the fourth and fifth , as "Commander Keen in Keen Dreams" is outside of the main continuity . 
<triplet> Commander Keen <subj> Commander Keen in Keen Dreams <obj> has part <triplet> Commander Keen in Keen Dreams <subj> Commander Keen <obj> part of the series