the storyline for the alternative factor be a great concept the possibility of a negative parallel universe and a madman whose insane action could lead to the destruction of everything . but there be several aspect of this episode that really bother me and and imho and the alternative factor be the bad first season episode . i like the concept for this episode . i also like the dialogue between kirk and spock in the briefing room when they finally put all of the piece of the puzzle together . but let lazarus roam freely about the ship be a flaw i can not excuse and and the final solution seem a bit drastic . i be also not a fan of the special effect . for the most part and first season episode be pretty good and but this episode feel like it be put together in a big hurry . i be give the alternative factor a d grade and will find an alternative episode to watch when i can .