"Friday's Child" spawns an exciting mixture of action and intrigue on a rugged planet hosting a fierce warrior people. D.C. Fontana's captivating script crams a movie's worth of adventure into a regrettably brief span, as a result the intricacy of Capellan politics gets confusing as Akaar, High Teer of the Ten Tribes, dies early in a violent coup. This forces the landing party to flee with his young wife Eleen, somewhat challenging the Prime Directive despite Kirk's impassioned words about the primacy of Earthman laws (that Capella belongs to the Capellans). Maybe the presence of the Klingons demands a more dynamic interpretation just like Kirk delivers!
The episode also features backstory about MackCoy in a series almost otherwise devoid of such information. By acting as Eleen's interface MackCoy receives plenty of attention, even including a savage spattering with a rock, poor reward for his impressive pre- and post-natal psychiatry. Back aboard Enterprise Mr. Scott handles the bridge capably with the captain and first officer away, not being fooled again by the Klingons (as advised by Russian folk-wisdom?) not to mention his red-shirted "cavalry over the hill" moment arriving in rescue. And Sulu sees the debut of his helm scanner!
Strong character performances reinforce the story. Michael Dante portrays the ambitious Maab as a respectable and effective leader. His self-sacrifice to draw the Klingon's fire is a testament to the nature of the Capellans. Julie Newmar reveals the opportunistic Eleen as not quite so untouchable. (For a people reputed for honest she lies quick enough to defend her new friends!) The personality of Akaar played by Ben Gage dominates during his few unfortunately short scenes. Tige Andrews as Kras is sufficiently nasty in tone and demeanor but may be one of the least threatening Klingons ever but of course, how bad must it be to draw this demeaning an assignment from the High Command?
The production values are simple but evocative including the colorful costumes of the Capellans and especially their krazy kool kligats. That's a neat (if inexplicable) trick with the communicators too, burying the entrance to their lair (and more than a few Capellans it seems) under an acoustically generated avalanche. The landing party avoids pursuit across a spectacular landscape towards a suspenseful climax of interspecies combat started by a Federation bow-fired "shot" that appears as much a surprise to the Klingon as well as the Capellans! OK, so maybe it could do without "ootchie wootchie cootchie coo" but beyond that it's a pretty good bargain for your rocks.