Simply put, "Halloween Knights" is sublime. The quick and dirty premise is also the most important factoid to delight in...Murdoc is BACK. Any episode with Murdoc is a MacGyver classic anyway, so you know from the get-go "Halloween Knights" is going to be good.
And it is and so much more, for not only is Murdoc back, complete with a new face (the other was horribly disfigured by multiple "deaths" by fire, explosion, falling, you name it), and living under a cemetery in Mac's part of town, he is supposedly walking the straight and narrow and needs Mac's help. You see, the maliciously murderous Murdoc actually has a soft-spot--his sister Ashton, who knows nothing of him, but has benefited through the years from his anonymous watchfulness (and prolly the occasional third-party check from H.I.T.). Anyway, since Murdoc has defected from H.I.T. (the concept of which we are first introduced to in this episode), H.I.T. hits back by taking away the only thing Murdoc cares about--Ashton. Since Mac is the best, 'doc needs his help in getting back his sister. "Why should I help you?" retorts Mac. Well MacGyver, because you're such a swell guy.
Ok, so it's Halloween as the title suggests, and to get Ashton back, Murdoc has been summonsed to an exclusive H.I.T. costume party, at which he will most likely endure and long and particularly sadistic retirement ritual, observed by a Royal Flush. But I'm getting ahead of myself.
MacGyver agrees to help Murdoc under a few conditions: That they do it Mac's way (no guns, no violence), and that once Ashton is found and freed, Murdoc will provide Mac with all he needs to know to shut H.I.T. down for good. To top it off, Murdoc is to turn himself in to the police, to pay for the lives he has taken and all the havoc his awesome badness has caused. Murdoc agrees, albeit a little reluctantly on the last one, and the terrific two-some set out to save the day (or night) by crashing the party.
This night is also the host of a top-secret board meeting of H.I.T. big-wigs, who are showing up dressed as a Royal Flush. Murdoc and Mac overtake the Joker and Mac shows up in full costume to dumb-it up at a bored meeting. Little did he know he would have to make a report, and hilariously stalls as Murdoc struggles to cut the power and "flush" him out of there.
Accelerating a bit, Mac and Murdoc make it to the killing fields (as I like to call them), the elaborate, automated shooting range created specifically for Murdoc, and stealthily make their way around machine guns with motion sensors and various other creative, MacGyver-worthy obstacles.
Lots of awesomely daring tricks and treats in this thrilling last few minutes, as MacGyver tiptoes his way through a pit of rainbow-colored vipers (with a snake-fearing Murdoc atop his shoulders!!) to save Ashton and ultimately the day. Or night. Or "Knight," for that matter. These two truly are the knights in this ep, an unlikely team making for a more than memorable episode of "MacGyver."
The end of the episode has Murdoc questionably dead (again), Ashton safe, and Murdoc coming through on his deal to end the antics of H.I.T.. As for turning himself in, well, did you ever think he would? An awesome MacGyver in every since...by season five writers had the formula down to a science, and "Halloween Knights" is a perfect example of how this show can get it so very, very right.