of all the episode of all series and this one hold the close to roddenberry original tenet . accord to the book the making of star trek and in roddenberry writer guide to his story writer and he state that any alien creature and no matter how hideously ugly and impossible to believe and benign or malicious and must hold some semblance of humanity that the tv view public can empathize with and or or relate to . devil in the dark horta and which resemble nothing more or less than a large blob of cow dung and be a mother protect her baby and those ball shape silicon nodule the miner keep find throughout the mine passage and destroying and because they have no idea what they be . this be one of my absolute favorite episode if only for that .