An intriguing setup, impressive visuals, and ominous sound design make this sci-fi creeper fitfully compelling, but the premise runs out of gas partway through, rendering it a bit of a slog. The film has a real Twilight Zone feel, particularly near the beginning, when a bemused Tom and Gemma discover that they're trapped in Yonder. The camera watches their white car from high above as it loops and meanders around the eerie grid of mint-colored houses, finding no escape. Later, the couple discovers a box labeled "Prospect Foods," full of vacuum-packed lamb chops and shelf-stable milk, which appears out of nowhere and disappears just as mysteriously, now filled with Tom and Gemma's dirty dishes. Tom and Gemma set up watch to see who or what is taking and delivering the boxes -- hoping to "bash their brains in" with the gardening equipment Tom brought in with them -- but the moment they look away, the box is gone.
Moments like this are eerie, to be sure, but there's a reason why the best Twilight Zone episodes are only half an hour long. That's just long enough to introduce characters, spring a strange surprise on them, and wrap things up tidily with no dead spots in the drama. A longer running time necessitates more plot, and Vivarium is lacking in that department. Another mysterious box delivers a human (or is it?) baby to the couple, with a note that reads "Raise the child and be released." But is this unnamed new character, who grows to the size of a second-grader in a few months and shrieks unnervingly when he's hungry or bored, really a child? And just what kind of "release" can Tom and Gemma expect when the "child" has reached adulthood? The answers are slow in coming. They're nicely unnerving when they arrive, but the wait will try most viewers' patience, leaving them to check out emotionally from Tom and Gemma's plight. Still, the sight of Yonder's mint-green rows of lookalike houses, the fluffy fake clouds above, and the unsettling grinding and squeaking noises on the soundtrack aren't easily forgotten, even if this film's too-light plotline may be.