This review may contain spoilers.

Only "Supernatural" would use the death of three of its recurring characters to illustrate the importance of family. In the end, each major character kills someone close to them, but they emerge from the experience with a better understanding of family.

Eve (Julia Maxwell ) resurfaces and releases a parasitic worm that moves from person to person, turning its victim into a killer. Before the worm is destroyed, Dean (Jensen Ackles) kills his cousin Gwen Campbell (Jessica Heafy), Sam (Jared Padelecki) murders his grandfather Samuel (Mitch Pileggi) and Bobby (Jim Beaver) kills his fellow hunter Rufus (Steven Williams). Somehow, releasing a worm is supposed to show us how great and powerful Eve, aka "The Mother of All," supposedly is.

And that, in the end, is the episode's fatal flaw. Eve simply didn't come across as menacing. Dressed in white and barefoot, she appeared pretty benign. The worm was small, but did big damage, but visually, it was nothing more than a minor irritant. Perhaps viewers were expected to pick up on the notion of everyone having a monster inside, but that idea was stifled by all the talk about the importance of family being preached by Dean.

With a several week hiatus coming up, this episode obviously meant to serve as some sort of denouement for this part of the season, but sadly, it fell flat. Aside from the death of a few secondary characters, none of whom will be missed, the episode was little more than mid-season filler.

Points Of Interest

1. The title of the episode, "And Then There Were None," is a reference to the classic Agatha Christie novel in which ten guests are invited to an isolated mansion, only to be killed off one by one. Despite the title, the episode bears almost no resemblance to Christie's novel.

2. Despite borrowing heavily from many different films over the year, including such highly regarded material as John Carpenter's "The Thing" (1982), nobody bothered to point this out. Dean is usually right on top of these pop culture references, but not this time.

What Worked

Each major character killed a family, or pseudo-family, member. It was a brutal episode that showed just how high the stakes are living the life of a hunter.

Finally, Samuel Campbell is dead. The character ceased being interesting once he betrayed the Winchester boys. I'm glad they didn't try to purse a redemption storyline.

What Didn't Work

We've seen this whole body switching monster before; while some might generously compare it to Carpenter's "The Thing," or even a little known but quite entertaining film called "The Hidden" (1987), it most closely resembled the underwhelming "Jason Goes to Hell" (1993).

Giving Credit Where Credit Is Due

"Supernatural" stars Jared Padalecki and Jensen Ackles. "And Then There Were None" was written by Brett Matthews (II). It was directed by Mike Rohl.

"Supernatural" airs Fridays at 9 p.m. ET on The CW.