I’ve become a fan of NCIS. I watch an episode almost every night. I like it. (I’m currently on season 7, so don’t worry about reading any spoilers for a recent episode.) Every once in a while, however, they come up with a plot that is so full of holes, it should never have seen airtime.

Case in point, this episode, called Code of Conduct. At the end the episode it is revealed that the murder was committed by the victim’s step-daughter, a short, teen-aged girl. She planned the murder and intended to frame her step-mother. She bought duct tape and a garden hose using her step-mother’s credit card and used those items in a somewhat clumsy attempt to make the murder look like a suicide. All of that is fine as far as it goes, but there are lots of details that do not make sense.

If you are going to take the trouble to deliberately murder someone, you certainly aren’t going to leave anything to chance. Along with your planning and preparation—making sure you have an alibi, throwing suspicion on someone else—you certainly will not neglect to use a method that will guarantee your victim ends up dead.

Now, don’t get me wrong. I have nothing but admiration for the writers of crime dramas tasked with coming up with ever more innovative, even bizarre, ways of divorcing souls from bodies. Nevertheless, I can’t help thinking that one crucial criterion for a planned murder is this: Is the plan certain to succeed? Does it depend too much on chance?

In this episode we are asked to believe that this girl was smart enough to make a plan to make her step-father’s death look like a suicide. She bought the necessary supplies. Yet the means she actually used to kill him was to bring him a thermos of liquid nitrogen, telling him it was coffee. She apparently gave no thought to the possibility that he would pour it into a cup before drinking it or that he would simply look at it and wonder why it didn’t look like coffee or that he might take a tentative sip (thinking it was hot) instead of taking a fatal gulp. It’s not that I can’t imagine a Marine gulping down coffee without looking at it. It’s that I can’t imagine a murderer relying on that behavior to commit the murder.

But that’s not all.

The murderer was discovered because she drove her dad’s car and left the seat adjusted for her small body. She brought him the fatal drink, waited until he was dead, then manhandled his six-foot corpse into the car parked in the driveway, attached the garden hose to the exhaust pipe and threaded it through the window and plugged the holes with duct tape. She did all this in the driveway where everything she did would be visible from the street. In fact, there were kids next door throwing TP into a tree and laughing the way only teen boys laugh, and they were the ones who discovered the Marine’s body. Again, it’s not that I can’t imagine a teen girl having the chutzpah to put a corpse in a car where any passerby could see it. It’s that I can’t imagine that being part of a well-designed plan.