After three successive "G.I. Joe" mini-series which culminated in the excruciating silliness of "Pyramid of Darkness", this lean, mean, no-nonsense potboiler was a refreshing change of pace. Christy Marx keeps the action sequences popping, with plenty of great character moments for both heroes and villains as the icing on the cake. Even the bit-part characters are vivid and memorable! This is also notable as one of the very few episodes where Storm Shadow was handled right. A morally ambiguous top star of the "G.I. Joe" comic book, he tended to come off very badly in the TV series, as either a coward or a caricature, or both. But not here!
I can't think of any other stand-alone first-season episode of "G.I. Joe" that is better than this one. Along with Buzz Dixon's 2-part "The Traitor" and Sharman DiVono's "Memories of Mara", it's in my personal "G.I. Joe" Top Three, a shining example of what the show should have been like more often, instead of wallowing in gimmickry and goofiness.
I don't begrudge Christy Marx the career advancement that "Jem" gave her, but "Jem"'s gain was "G.I. Joe"'s loss. She only wrote four more segments, both 2-parters -- "Synthoid Conspiracy" and "Captives of Cobra." Both have their merits, but "Countdown for Zartan" was Christy Marx at her best.