Nutshell: Very bizarre, but it works. Scores points for being different, featuring intriguing surreal qualities.
The Voyager crew comes across a planet that has been destroyed by a natural disaster. Janeway beams up from under the planet's surface a five-person computer-controlled biological stasis system protecting the few remaining survivors of the colony that had been wiped out because of the disaster 19 years earlier.
According to a recorded message, the system was scheduled to revive the survivors four years ago. But for unknown reasons the survivors have not reawakened, and equally puzzling is why two of the five aliens are dead. There is no evidence of a malfunction or system failure. Ensign Kim studies the system and discovers the survivors' brains are all active—in a sort of 19-year-long dream state monitored by the computer system. Because pulling the plug and forcing the aliens out of their stasis could cause irrevocable brain damage, Janeway approves another option: Torres and Kim themselves go into bio-stasis to communicate with the computer system and the other alien survivors.
What they find on the other side is a strange, surreal, carnival world run by a crazed entity known only as the Clown (Michael McKean). The Clown is a computer-manufactured character comprising the aliens' fear of their own situation. In essence, the Clown has become fear itself—and holds the aliens hostage in the fantasy world. He has but one demand—to exist. Like Professor Moriarty (of TNG's "Elementary, Dear Data," "Ship in a Bottle"), the Clown is a computer simulation that has somehow taken on a sentient awareness and a desire to exist. Unfortunately, he exists only in the hostages' minds. If they were to leave, he would cease to exist.
He has the ability to literally kill the hostages by "scaring them to death" and causing deadly heart attacks. In the fantasy world, this is symbolically represented as the Clown executing the hostages via guillotine. (This is precisely what he did to the two dead aliens.) Another strike against Kim, Torres, and the hostages is the fact that the Clown can read minds (since he's tied directly into their minds through the computer). Now that Torres and Kim have shown up, the Clown demands that they stay—threatening to kill one of his hostages if they leave.
Yes, this was written by Joe Menosky, the guy renowned for his very weird concepts. And, yes, "The Thaw" is fairly weird. It's an effective mix of colorful goofiness and some interesting arguments surrounding the question of how to defeat fear itself. The weirdness is evident in the surreal production design of the Clown's fantasy world, and its population of circus-like characters and distinctive, geometrical objects.
The Clown, while a pretty funny guy, is obviously demented and unstable, and has a mocking nature that tends to push the other characters' buttons. Like with Q, everything is a joke to him (although B'Elanna and Harry are most definitely not amused), but at the same time, he will resort to deadly force when he feels his existence threatened. McKean is perfect for the role, bringing just the right mix of annoying humor and buried depth to the character.
The Clown agrees to release Torres so she can take his message of intent back to Janeway. Subsequent communications bring Doc into the picture, since he cannot be held hostage by the Clown. Some of the show's funniest moments involve Picardo and McKean facing off with their arsenals of dry sarcasm. Other scenes feature humor that is just downright bizarre. Take, for example, a scene of building intensity where the Clown is about to perform "surgery" on Harry but is suddenly interrupted by the Doctor, who appears out of nowhere and immediately says something that changes the entire mood of the scene. Another goofy laugh comes during Doc's delivery of Janeway's ultimatum for surrender: The clown and his entire group of misfits break into unrestrained laugher at Doc's notion, then stop on cue just as abruptly as they started. Very weird, but also very amusing.
The episode has a sense that might best be described as somewhere in the realm of Alice in Wonderland. While the Clown and his characters are cartoonish, they still manage to come across as fairly threatening. (In fact, the only missed opportunity is that the writers fail to supply the Clown with the line "Off with their heads!")
Although much of "The Thaw" is unrestrained dementia, there is also a solid story percolating somewhere in here. The last act in particular finds success in evaluating fear and its intangible qualities. Janeway's analysis of the topic is particularly well-written. The questions she raises ("Isn't there more to fear than a simple demand to exist? Why do people enjoy dangerous sports or holodeck adventures with the safety off? Why, after all these centuries, do children still ride on roller coasters?") make a lot of sense, and contribute a believable, logical line toward the episode's denouement. The conclusion, where Janeway tricks the Clown into releasing the hostages in exchange for herself—revealing later that she is merely a holographic image—is a neat gimmick that makes a surprising amount of sense under the circumstances. Particularly impressive is the final thirty seconds of the show, as the Clown fades away into nothingness as Janeway remarks that fear's only reason for existence is to be overcome—such that it eventually vanishes.
This episode is a pleasant surprise. It manages to be goofy, strange, and humorous, and still holds up to a reasonable amount of scrutiny. I'll have to admit that the madcap nature that seemed to be imminent once the characters entered this bizarro world had me in a certain dread at first. (It's hard to execute concepts like this without looking quite silly.) But, fortunately, "The Thaw" pulls everything together and makes it worthwhile.