The final NightShade solo tale has a kool "Easter Egg"...
...let's see if you can pick it out!
(Note: Unlike Marvel or DC, Charlton didn't tend to use footnotes referring to other issues.)
Jewelee (also a Kaler/Steve Ditko creation) was part of a duo who faced NightShade and Captain Atom in an earlier issue.
Charlton's Captain Atom #89 (1967) was the final issue of the series.
While a Captain Atom book-length tale had been penciled and plotted (and finally saw publication in the 1970s), no further NightShade stories were prepared beyond a few story notes continuing this arc.
BTW, while the main stories (starring Captain Atom) from these issues of Captain Atom were reprinted in DC Action Hero Archive hardcovers, the NightShade backup tales were not!