Tethered starts with an adrenaline-pumping premise: You, Charles, are climbing a snowy mountain. You are roped to your partner Judith, when she slips and falls into a crevasse. What do you do? Well, there's really only one thing you can do. Then the game proper truly starts.
Most of Tethered takes place in a cave on a mountainside. This is a classic IF setting and so can often feel stale, but the premise of Tethered makes it come across as natural and fresh - more of a nod to IF's roots in Colossal Cave than something derivative.
Gameplay-wise, there are a couple of clever puzzles involving a rope that can be stretched between multiple rooms. One of these puzzles has an alternate solution that I found by looking at the walkthrough after I finished the game; this alternate solution may remind some players of a prominent puzzle in a prominent game from last year's IFComp. Also, I love the game's solution to the problem of navigating a cave in the dark: It's completely intuitive yet fairly original from an IF standpoint.
Like several other games from this year's IFComp, as you play Tethered further you realize that there is more going on here than appears at first. The ending is poignant and moving - and it adds a powerful twist on the game's name: "Tethered."
Make sure you check out the game's response to XYZZY.
Finally, a word about the language: Tethered is the first game in the author's new IF-writing language Dialog. It looks impressive to me so far. In particular, the rope-between-multiple-rooms feature is apparently a difficult one to implement in most traditional parser languages. The fact that it works smoothly in Tethered indicates something about the complexity of Dialog.
Overall, I found Tethered to be yet another of the many strong dramas in this year's IFComp.